How to Build Great React Search Experiences Quickly

How to Build Great React Search Experiences Quickly

How to Build Great React Search Experiences Quickly.We'll walkthrough how to build excellent, React-based search experiences using Elastic's open source Search UI library

Building search experiences is hard work. It can seem easy at a glance: build a search bar, put data into a database, then have user input fuel queries against the database. But there are many things to consider in the data modeling, underlying logic and — of course — the overall design and user experience.

We’ll walkthrough how to build excellent, React-based search experiences using Elastic’s open source Search UI library. It’ll take about 30 minutes and afterwards you’ll be ready to bring search to any application.

But first, what is it that makes building search so challenging?

Search Is Hard

A great article made the rounds a few weeks ago titled Falsehoods Programmers Believe About Search. It contains an exhaustive list of false assumptions developers take into the development of search.

Among the many believed falsehoods:

  • “Customers who know what they are looking for will search for it in the way you expect”
  • “You can write a query parser that will always parse the query successfully”
  • “Once setup, search will work the same way for the next week”
  • “Synonyms are easy”
  • … And many others gems — you should give it a read!

The takeaway is that search has many challenges — and they aren’t just under-the-hood. You need to think about how to manage state, build components for filtering, faceting, sorting, pagination, synonyms, language processing, and much, much… much more. But, in summary:

Building great search requires two sophisticated parts: (1) the search engine, which provides APIs to power search and (2) the search library, which paints the search experience.

For the search engine, we’ll look at Elastic App Search.

For the search experience, we’ll introduce an OS search library: Search UI.

When we’re done, it’ll lookjust like this:

Search Engine: Elastic App Search

App Search is available as either a paid, managed service, or a free, self-managed distribution. We’ll use the managed service for this tutorial, But remember that your team can use Search UI and App Search with a basic license at no cost if you host it yourself.

The plan: index documents which represent the best video games of all time into a search engine, then design and optimize a search experience to search through them.

First, signup for a 14 day trial — no credit card needed.

Create an Engine. You can pick from 13 different languages.

Let’s name it video-games and set the language to English.

Download the best video games data set and then upload it to App Search using the importer.

Next, click into the Engine, then select the Credentials tab.

Create a new Public Search Key with Limited Engine Access to only the video-games engine.

Retrieve the new Public Search Key and your Host Identifier.

Even though it didn’t look like much, we now have a fully functioning search engine that’s ready to search through our video game data using a refined search API.

Here’s what we’ve done so far:

  • Created a search engine.
  • Ingested documents.
  • Created a default schema.
  • Retrieved a scoped, disposable credential that we can expose to the browser.

That’s it for App Search, for now.

Let’s get to building our search experience using Search UI.

Search Library: Search UI

We’re going to use the [create-react-app](https://github.com/facebook/create-react-app) scaffolding utility to create a React app:

npm install -g create-react-app
create-react-app video-game-search --use-npm
cd video-game-search

Within this foundation, we’ll install Search UI and the App Search connector:

npm install — save @elastic/react-search-ui @elastic/search-ui-app-search-connector

And start the app in development mode:

npm start

Open up src/App.js in your favourite text editor.

We’ll start with some boilerplate code, and then unpack it.

Mind the comments!

// Step #1, import Statements
import React from "react";
import AppSearchAPIConnector from "@elastic/search-ui-app-search-connector";
import { SearchProvider, Results, SearchBox } from "@elastic/react-search-ui";
import { Layout } from "@elastic/react-search-ui-views";
import "@elastic/react-search-ui-views/lib/styles/styles.css";
// Step #2, The Connector
const connector = new AppSearchAPIConnector({
  searchKey: "[YOUR_SEARCH_KEY]",
  engineName: "video-games",
  hostIdentifier: "[YOUR_HOST_IDENTIFIER]"
});
// Step #3: Configuration Options
const configurationOptions = {
  apiConnector: connector
  // Let's fill this in together.
};
// Step #4, SearchProvider: The Finishing Touches.
export default function App() {
  return (
    <SearchProvider config={configurationOptions}>
      <div className="App">
        <Layout
        // Let's fill this in together.
        />
      </div>
    </SearchProvider>
  );
}
Step 1: import Statements

We’ll need to import our Search UI dependencies and React.

The core components, connector, and view components are contained within three different packages: @elastic/search-ui-app-search-connector, @elastic/react-search-ui, and @elastic/react-search-ui-views. We’ll learn more about each of them as we proceed.

import React from "react";
import AppSearchAPIConnector from "@elastic/search-ui-app-search-connector";
import { SearchProvider, Results, SearchBox } from "@elastic/react-search-ui";
import { Layout } from "@elastic/react-search-ui-views";
import "@elastic/react-search-ui-views/lib/styles/styles.css";

We’ll also be importing a default stylesheet for this project, which will give us a nice look and feel without writing a line of our own CSS:

import "@elastic/react-search-ui-views/lib/styles/styles.css";
Step 2: The Connector

We have our Public Search Key and Host Identifier from App Search.

Time to put them to work!

The connector object within Search UI uses the credentials to hook into App Search and power search:

const connector = new AppSearchAPIConnector({
  searchKey: "[YOUR_SEARCH_KEY]",
  engineName: "video-games",
  hostIdentifier: "[YOUR_HOST_IDENTIFIER]"
});

Search UI works with any search API. But connectors make it so that a search API will “just work”, without any deeper configuration.

Step 3: configurationOptions

Before we dig into configurationOptions, let’s take a moment to reflect.

We imported a set of data into our search engine. But what kind of data is it?

The more we know about our data, the better we’ll understand how to present that data to searchers. And that’ll inform how to configure the search experience.

Let’s look at one object, the best object of all within this data set:

{
  "id": "final-fantasy-vii-ps-1997",
  "name": "Final Fantasy VII",
  "year": 1997,
  "platform": "PS",
  "genre": "Role-Playing",
  "publisher": "Sony Computer Entertainment",
  "global_sales": 9.72,
  "critic_score": 92,
  "user_score": 9,
  "developer": "SquareSoft",
  "image_url": "https://r.hswstatic.com/w_907/gif/finalfantasyvii-MAIN.jpg"
}

We see that it has several text fields like name, year, platform, and so on and some number fields like critic_score, global_sales, and user_score.

If we ask three key questions, we’ll know enough to build a solid search experience:

  1. How will most people search? By the name of the video game.
  2. What will most people want to see in a result? The name of the video game, its genre, publisher, scores, and its platform.
  3. How will most people filter, sort, and facet? By score, genre, publisher, and platform.

We then can translate those answers into our configurationOptions:

const configurationOptions = {
  apiConnector: connector,
  searchQuery: {
    search_fields: {
      // 1. Search by name of video game.
      name: {}
    },
    // 2. Results: name of the video game, its genre, publisher, scores, and platform.
    result_fields: {
      name: {
        // A snippet means that matching search terms will be highlighted via <em> tags.
        snippet: {
          size: 75, // Limit the snippet to 75 characters.
          fallback: true // Fallback to a "raw" result.
        }
      },
      genre: {
        snippet: {
          size: 50,
          fallback: true
        }
      },
      publisher: {
        snippet: {
          size: 50,
          fallback: true
        }
      },
      critic_score: {
        // Scores are numeric, so we won't attempt to snippet these, we'll just use the raw
        // value.
        raw: {}
      },
      user_score: {
        raw: {}
      },
      platform: {
        snippet: {
          size: 50,
          fallback: true
        }
      },
      image_url: {
        raw: {}
      }
    },
    // 3. Facet by scores, genre, publisher, and platform, which we'll use to build filters later.
    facets: {
      user_score: {
        type: "range",
        ranges: [
          { from: 0, to: 5, name: "Not good" },
          { from: 5, to: 7, name: "Not bad" },
          { from: 7, to: 9, name: "Pretty good" },
          { from: 9, to: 10, name: "Must play!" }
        ]
      },
      critic_score: {
        type: "range",
        ranges: [
          { from: 0, to: 50, name: "Not good" },
          { from: 50, to: 70, name: "Not bad" },
          { from: 70, to: 90, name: "Pretty good" },
          { from: 90, to: 100, name: "Must play!" }
        ]
      },
      genre: { type: "value", size: 100 },
      publisher: { type: "value", size: 100 },
      platform: { type: "value", size: 100 }
    }
  }
};

We’ve connected Search UI to our search engine and now we have options that govern how we’re going to search through data, display our results, and then explore those results. But we need something to tie everything to the dynamic frontend components of Search UI.

Step 4: SearchProvider

The object that rules them all; the SearchProvider is where all other components are nested.

Search UI provides a Layout component, which is used to paint a typical search layout. There are deep customization options, but we won’t go into those in this tutorial.

We will do two things:

  1. Pass in configurationOptions to SearchProvider.
  2. Place some structural building blocks into Layout and add two basic components: SearchBox and Results.
export default function App() {
  return (
    <SearchProvider config={configurationOptions}>
      <div className="App">
        <Layout
          header={<SearchBox />}
          // titleField is the most prominent field within a result: the result header.
          bodyContent={<Results titleField="name" urlField="image_url" />}
        />
      </div>
    </SearchProvider>
  );
}

At this point, we have the basics set up on the front-end. There’s a few more details to work out on the back-end before we can run this. We should also work on the relevance model so that search is fine tuned for the unique needs of this project.

Off to App Search ~

Back to the Lab

App Search has powerful and refined search engine features. It makes once-sophisticated tuning much more enjoyable. We can perform fine-grained relevance adjustments and seamless schema changes in a few clicks.

We’ll adjust the schema first to see it in action.

Login to App Search, enter the video-games Engine, and then click Schema under the Manage section.

The schema appears. Each of the 11 fields is considered text by default.

In the configurationOptions object, we’ve defined two range facets to help us search through numbers: user_score and critic_score. For a range facet to work as expected, the field type needs to be a number.

We also might want to do some boosting and relevance tuning based on numerical values.

Click on the drop down menu next to each field, change it to number, then click Update Types:

The Engine re-indexes on the fly. And later on — when we add the faceting components to our layout — the range filters will function as we expect.

And now, onto the real nifty stuff.

This Section Is Highly Relevant

There are three key relevance features: Synonyms, Curations, and Relevance Tuning.

Select each feature under the Search Settings section in the sidebar:

Synonyms

Some people drive cars, some automobiles, others might drive a jalopy. The internet is global and people around the globe use different words to describe things. Synonyms help you create sets of terms that are considered one and the same.

In the case of a video game search engine, we know people will want to find Final Fantasy. But maybe they’ll type FF instead.

Click into Synonyms, then select Create a Synonym Set and enter the terms:

Click Save. You can add as many synonym sets as you’d like.

Searches for FF will now carry the same weight as searches for Final Fantasy.

Curations

Curations are a favorite. What if someone does search for Final Fantasy or FF? There are many games in the series — which will they get?

By default, the top five results looks like so:

  1. Final Fantasy VIII
  2. Final Fantasy X
  3. Final Fantasy Tactics
  4. Final Fantasy IX
  5. Final Fantasy XIII

That doesn’t seem right… Final Fantasy VII was the best Final Fantasy game of all. And Final Fantasy XIII wasn’t very good! 😜

Can we make it so that someone searching for Final Fantasy will receive Final Fantasy VII as the first result? And can we remove Final Fantasy XII from our search results?

We can!

Click into Curations and enter a query: Final Fantasy.

Next, drag the Final Fantasy VII document up to the Promoted Documents section by grabbing the handlebar on the leftmost side of the table. And then click on the Hide Result button on the Final Fantasy XIII document — the eye with the line going through it:

Anyone performing a search for Final Fantasy or FF will now see Final Fantasy VII first.

… And they won’t see Final Fantasy XIII. Hah!

We can promote and hide many documents. We can even sort promoted documents so we maintain full control over what appears at the top of each query.

Relevance Tuning

Click on Relevance Tuning in the sidebar.

We search into one text field: the name field. But what if we have multiple text fields people will search through, like a name field and a description field? The video game data set we’re using does not contain a description field, so we’ll fake some documents to think through it.

Say our documents looked similar to this:

{ 
  "name":"Magical Quest",
  "description": "A dangerous journey through caves and such." 
},
{ 
  "name":"Dangerous Quest",
  "description": "A magical journey filled with magical magic. Highly magic." 
}

If someone wanted to find the game Magical Quest, they would enter that as the query. But the first result would be Dangerous Quest:

Why? Because the word “magical” is present three times in the description of Dangerous Quest and the search engine will not know that one field is more important than another. It will then rank Dangerous Quest higher. This conundrum is why Relevance Tuning exists.

We can select a field and — among other things — increase the weighting of its relevance:

We see that when we scale up weight, the right item — Magical Quest — rises to the top because the name field becomes more significant. All we need to do is drag the slider to a higher value and click Save.

We’ve now used App Search to:

  1. Adjust the schema and change user_score and critic_score to number fields.
  2. Fine-tune the relevance model.

And that concludes the fancy “dashboard” features — each one has a matching API endpoint which you can use to make things work programmatically if GUIs aren’t your thing.

Now, let’s finish off the UI.

Finishing Touches

At this point your UI should be functional. Try some queries and poke around. The first thing that jumps out is that we’re missing tools to explore our results, like filtering, faceting, sorting, and so on, but search works. We’ll need to flesh out the UI.

Within the initial src/App.js file, we imported three basic components:

import { SearchProvider, Results, SearchBox } from "@elastic/react-search-ui";

Let’s add some more, given what we’ve defined for our configuration options.

Importing the following components will enable the missing abilities within the UI:

  • PagingInfo: Display information on the current page.
  • ResultsPerPage: Configure how many results appear on each page.
  • Paging: Navigate through different pages.
  • Facet: Filter and explore data in ways unique to the type of data.
  • Sorting: Re-orient results for a given field.
import {
  PagingInfo,
  ResultsPerPage,
  Paging,
  Facet,
  SearchProvider,
  Results,
  SearchBox,
  Sorting
} from "@elastic/react-search-ui";

Once imported, components can be placed into the Layout.

The Layout component divides the page into sections and components can be placed into these sections via props.

It contains sections for the:

  1. header: Search box/bar.
  2. bodyContent: Result container .
  3. sideContent: Sidebar which contains facets and sorting options.
  4. bodyHeader: “Wrapper” around results with context rich information like current page, number of results per page.
  5. bodyFooter: Paging options for quick navigation between pages.

Components render data. Data is fetched based on the search settings we provided in the configurationOptions. Now, we’ll place each component in the appropriate Layout section.

For example, we described 5 faceting dimensions in configurationOptions, so we’ll create 5 Facet components. Each Facet component will use a field prop as a key back to our data.

We’ll put them in the sideContent section, along with our Sorting component, then place the Paging, PagingInfo, ResultsPerPage components in the sections that best suites them:

<Layout
  header={<SearchBox />}
  bodyContent={<Results titleField="name" urlField="image_url" />}
  sideContent={
    <div>
      <Sorting
        label={"Sort by"}
        sortOptions={[
          {
            name: "Relevance",
            value: "",
            direction: ""
          },
          {
            name: "Name",
            value: "name",
            direction: "asc"
          }
        ]}
      />
      <Facet field="user_score" label="User Score" />
      <Facet field="critic_score" label="Critic Score" />
      <Facet field="genre" label="Genre" />
      <Facet field="publisher" label="Publisher" isFilterable={true} />
      <Facet field="platform" label="Platform" />
    </div>
  }
  bodyHeader={
    <>
      <PagingInfo />
      <ResultsPerPage />
    </>
  }
  bodyFooter={<Paging />}
/>

Now let’s have a look at the search experience in the local development environment.

Much better! We have rich options to explore the search results.

We threw in a couple extra goodies like multiple sort options and we’ve made the publisher facet filterable by adding a single flag. Try a search with a blank query and explore all the options.

Finally… let’s look at one last feature of the search experience. It’s a popular one…

Autocomplete.

You Autocomplete Me

Searchers love autocomplete because it provides instant feedback. Its suggestions come in two flavors: result and query. Depending on which flavor, a searcher will receive relevant results or potential queries that can lead to results.

We’re going to focus on autocomplete as a form of “query suggestion”.

This requires two quick changes.

First, we need to add autocomplete to the configurationOptions object:

const configurationOptions = {
  // ...
  autocompleteQuery: {
    suggestions: {
      types: {
        documents: {
          // Which fields to search for suggestions.
          fields: ["name"]
        },
        // How many suggestions appear.
        size: 5
      }
    }
  }
  // ...
};

Second, we need to enable autocomplete as a function of the SearchBox:

// ...
<Layout
  // ...
  header={<SearchBox autocompleteSuggestions={true} />}
/>
// ...

Yep — that’s it.

Try searching — as you type, autocomplete query suggestions appear.

Summary

We now have a good looking, functional search experience. And we’ve avoided a whole mess of pitfalls that often catch people as they try to implement search. Not bad for 30 minutes, wouldn’t you say?

Search UI is a flexible, modern React framework for the quick development of search experiences. Elastic App Search is a robust search engine built atop Elasticsearch. It’s a paid, managed service or you can run it yourself free with an ample basic license.
We’d love to see what you build with Search UI.
Stop by Gitter and consider contributing to the project!

Pagination in ReactJs

Pagination in ReactJs

There are a lot of resourceful materials online that give good insights into pagination in ReactJs, as well as NPM packages you can easily use

There are a lot of resourceful materials online that give good insights into pagination in ReactJs, as well as NPM packages you can easily use. As much as I appreciate those materials and love to use those packages, they mostly deal with loading the whole dataset on the page first then completely handle the pagination in the frontend. I am approaching this article with the concept of loading the exact data needed on the page, then manually loading other dataset based on the request when the user clicks the pagination number display. Below is the content structure to guide us through this article:

Table of Contents
  • Project Setup
  • HTML and CSS Styling
  • Pagination Data Format
  • Sample API request
  • Displaying the initial data
  • Showing Page Number and getting Other data
Project Setup

We are going to use create-react-app v0.1.0 which has the CSS Module configured already. Open your terminal and cd to the folder you want the project installed. Then run the below command:

npx create-react-app pagination  --use-npm

The above command will download the project into the folder calledpagination. You need to cd into the folder and run npm start. If everything goes well, you will have a page that looks like below:

HTML and CSS Styling

Open the project in your favorite code editor and locate the App.js file, We need to prepare our App.js to the look exactly like the way we want it by adding the HTML code and CSS style below:

Create a new file called App.module.css in the same directory where you have your App.js, then import it into your App.js using:

import styles from './App.module.css';

I want us to handle the display of the pagination number first, below is the style and HTML structure of what we are going to use.

  render() {
    

    return (
      <div className={styles.app}>
        
        <table className={styles.table}>
          <thead>
            <tr>
              <th>S/N</th>
              <th>First Name</th>
              <th>Last Name</th>
            </tr>
          </thead>
          <tbody>
              <tr>
                <td>1</td>
                <td>Abel</td>
                <td>Agoi</td>
              </tr>
              <tr>
                <td>2</td>
                <td>Muyiwa</td>
                <td>Aregbesola</td>
              </tr>
              <tr>
                <td>3</td>
                <td>Opeyemi</td>
                <td>Agoi</td>
              </tr>
              <tr>
                <td>4</td>
                <td>Ope</td>
                <td>Aina</td>
              </tr>
          </tbody>
        </table>


        <div className={styles.pagination}>
          <span>&laquo;</span>
          <span className={styles.active}>1</span>
          <span>2</span>
          <span>3</span>
          <span>4</span>
        </div>

      </div>
    );
  }

pagination_01.js

Add the content below into your App.module.css.

.app {
    width: 50%;
    margin: 0 auto;
}

table {
  border-collapse: collapse;
  border-spacing: 0; 
}


table {
  border-collapse: separate;
  border-spacing: 0;
  color: #4a4a4d;
  font: 14px/1.4 "Helvetica Neue", Helvetica, Arial, sans-serif;
  width: 100%;
}
tr {
  overflow-x: scroll;
}
th,
td {
  padding: 15px 15px;
  vertical-align: middle;
  /* text-align: left; */
}
thead {
  font-size: 14px;
  line-height: 24px;
  font-family: Lato;
  border: 1px solid transparent;

  max-width: 100%;
  font-weight: 900;
  line-height: 24px;
  mix-blend-mode: normal;

  color: rgba(51, 51, 51, .5);
  background: rgba(255, 255, 255, .9);
}
thead tr th {
  padding: 15px 15px;
  border: 1px solid transparent;


  text-align: left;
}
tbody {
  max-width: 100%;
}
tbody tr:nth-child(odd) {
  background: #f0f0f2;
}
tbody tr:hover {
  background: #f0f0f2;
}
td {
  padding: 15px 15px;
}
td:first-child {
}


.pagination {
    margin-top: 25px;
}
.pagination span {
  cursor: pointer;
  color: black;
  float: left;
  padding: 8px 16px;
  text-decoration: none;
  transition: background-color .3s;
  border: 1px solid #ddd;
}

.pagination span.active {
  background-color: #0099FF;
  color: white;
  border: 1px solid #0099FF;
}

pagination_app.module.css

Sorry for the plenty code written so far :), I want us to have a good looking table with pagination style in place before we move into the actual paging. If everything goes well, your view should look like below:

Pagination Data Format

In most cases, when you are making API calls to an endpoint that returns a paginated data, you need to pass at least the page number with the URL, hence a sample URL will look like below:

https://reqres.in/api/users?page=2

The most important thing to take note of in the URL above is the page=2 where 2 is the page number dataset we want to get. It can be 3,4 or any number as much as the dataset we have in the backend.

The response will always contain three important data which are per_page, total and the actual data we want to loop through. A sample response looks like below:

Sample API request

Talking about making an API request to the backend, We need a backend to make the request to, I decide to use https://reqres.in/ as the API endpoint for this tutorial because it is free, always available and reliable. You can decide to make your API request directly inside your component’s ComponentDidMount() or dispatch an action to redux from your ComponentDidMount() but for the purpose of this tutorial, we are going to make the API call from the App.js componentDidMount().

Firstly, we need to set the component’s state like below inside your App.js

  state = {
    users: null,
    total: null,
    per_page: null,
    current_page: null
  }

pagination_component_state.js

users is going to be the data we are going to loop over, while total and per_page is going to help us with calculating paging logic while the current_page will be used to style the active pagination link.

The next thing we should do is create a helper method that will serve the purpose of making an HTTP request to the API endpoint and also update the state with the response data. The method will look like below:

  makeHttpRequestWithPage = async pageNumber => {
    let response = await fetch(`https://reqres.in/api/users?page=${pageNumber}`, {
      method: 'GET',
      headers: {
        'Accept': 'application/json',
        'Content-Type': 'application/json',
      },
    });

    const data = await response.json();

    this.setState({
      users: data.data,
      total: data.total,
      per_page: data.per_page,
      current_page: data.page,
    });
  }

pagination_http_request.js

This method will accept a parameter called pageNumber so it can be reusable and will always update the state with the right data when the response is successful.

Since on page load, we need to make the HTTP request to the backend, and we are going to do this inside thecomponentDidMount() by calling the method above and passing it the first-page number we want which should be 1. Hence, the componentDidMount() will look like below:

 componentDidMount() {
    this.makeHttpRequestWithPage(1);
  }

pagination_componentDidMount.js

If we add console.dir(this.state.users) inside the render() method, below will be printed in the console

The null was before the data arrived, once the data arrived, it updates the state, hence the array of users data.

Displaying the initial data

Haven gotten the data needed, we need to loop through the data and display it. Hence we can update our render method to have below:

    let users;

    if (this.state.users !== null) {
      users = this.state.users.map(user => (
        <tr key={user.id}>
          <td>{user.id}</td>
          <td>{user.first_name}</td>
          <td>{user.last_name}</td>
        </tr>
      )); 
    }
    
    return (
      <div className={styles.app}>
        
        <table className={styles.table}>
          <thead>
            <tr>
              <th>S/N</th>
              <th>First Name</th>
              <th>Last Name</th>
            </tr>
          </thead>
          <tbody>
              { users }
          </tbody>
        </table>


        <div className={styles.pagination}>
          <span>&laquo;</span>
          <span className={styles.active}>1</span>
          <span>2</span>
          <span>3</span>
          <span>4</span>
          <span>&raquo;</span>
        </div>

      </div>
    );

gistfile1.txt

I replaced the dummy data we had inside the with the result of the loop which I equated to users. We have the assurance that when the state changes, ReactJs will automatically update the content of the table. The final stage is displaying the page logic and getting the other contents based on the page number clicked which will be sent to the API endpoint.

Showing Page Number and getting other data

Before we talk about showing page number automatically using the desired logic, I want us to manually show those numbers and make the actual API calls when the numbers are clicked. For now, we are going to hard code the pagination numbers ourselves like below:

<div className={styles.pagination}>
  <span onClick={() => this.makeHttpRequestWithPage(1)}>1</span>
  <span onClick={() => this.makeHttpRequestWithPage(2)}>2</span>
  <span onClick={() => this.makeHttpRequestWithPage(3)}>3</span>
  <span onClick={() => this.makeHttpRequestWithPage(4)}>4</span>
</div>

pagination_hard_code.js

The above code will look like below when previewed in the browser.

Notice that each span has an event handler attached to it, and I passed the page number to that event handler, so anytime we click on the pagination link, it will make a new HTTP request and update the component states, hence the user’s table data. We do not want to hard-code the links as we did above, so we need to automatically display those links.

So we’re planning on showing the page numbers for a series of pieces of data so that users can easily navigate multiple items. There are a few things that we need to know first:

  • The page that we’re on
  • Total number of items
  • Number of items per page

Good news is that we have captured all these things in our component’s state.

Next, we need to look at how we want to display the page numbers, there is a wide range of methods that people use:

  • Simple Next/Previous buttons with no numbers
  • A list of all possible pages
  • Page 1 & the last page, with the current page (and 2 above/below) shown

I personally prefer to show the very first page, that last page, and then the current page with 2 pages above & below. So for example on page 12 out of 24 pages we’d see:

1, 10, 11, 12, 13, 14, 24

This allows users to quickly navigate to the start, and to the end, as well as jump through multiple pages at once. For the purpose of this tutorial, I am going to show us how to show a list of all possible pages(item two above) then item three too.

The Arithmetic

We need to work out the total number of pages, for this, we want to take the total number of items that there are, and divide it by the number of items per page. But we want to make sure that we take that number and round it up.

So if there were 12 items in total, and we were showing 5 per page, we’d have a total of 3 pages of items. If we were to show 3 per page, we’d show 4 pages.

const pageNumbers = [];
for (let i = 1; i <= Math.ceil(this.state.meta.total / this.state.meta.per_page); i++) {
    pageNumbers.push(i);
}

page_logic_pagination.js

Haven gotten the page numbers, we need to loop through to display the span since we want to show all possible numbers first, our loop will look like below:

renderPageNumbers = pageNumbers.map(number => {
  let classes = this.state.current_page === number ? styles.active : '';

  return (
    <span key={number} className={classes} onClick={() => this.makeHttpRequestWithPage(number)}>{number}</span>
  );
});

pagination_all_numbers_loop.js

We need to update our pagination view to look like below:

<div className={styles.pagination}>
  <span onClick={() => this.makeHttpRequestWithPage(1)}>&laquo;</span>
  {renderPageNumbers}
</div>

pagination_view._01js

Congrats, we have successfully handle pagination, make HTTP request to the backend and changing the table content when user click on the page number to see.

To be sure we are on the same page, my App.js code looks like below:

import React, { Component } from 'react';
import styles from './App.module.css';

class App extends Component {


  state = {
    users: null,
    total: null,
    per_page: null,
    current_page: 1
  }


  componentDidMount() {
    this.makeHttpRequestWithPage(1);
  }


  makeHttpRequestWithPage = async pageNumber => {
    const response = await fetch(`https://reqres.in/api/users?page=${pageNumber}`, {
      method: 'GET',
      headers: {
        'Accept': 'application/json',
        'Content-Type': 'application/json',
      },
    });

    const data = await response.json();

    this.setState({
      users: data.data,
      total: data.total,
      per_page: data.per_page,
      current_page: data.page
    });
  }


  render() {

    let users, renderPageNumbers;

    if (this.state.users !== null) {
      users = this.state.users.map(user => (
        <tr key={user.id}>
          <td>{user.id}</td>
          <td>{user.first_name}</td>
          <td>{user.last_name}</td>
        </tr>
      ));
    }

    const pageNumbers = [];
    if (this.state.total !== null) {
      for (let i = 1; i <= Math.ceil(this.state.total / this.state.per_page); i++) {
        pageNumbers.push(i);
      }


      renderPageNumbers = pageNumbers.map(number => {
        let classes = this.state.current_page === number ? styles.active : '';

        return (
          <span key={number} className={classes} onClick={() => this.makeHttpRequestWithPage(number)}>{number}</span>
        );
      });
    }

    return (


      <div className={styles.app}>

        <table className={styles.table}>
          <thead>
            <tr>
              <th>S/N</th>
              <th>First Name</th>
              <th>Last Name</th>
            </tr>
          </thead>
          <tbody>
            {users}
          </tbody>
        </table>


        <div className={styles.pagination}>
          <span onClick={() => this.makeHttpRequestWithPage(1)}>&laquo;</span>
          {renderPageNumbers}
          <span onClick={() => this.makeHttpRequestWithPage(1)}>&raquo;</span>
        </div>

      </div>
    );
  }

}

export default App;

pagination_app.js

and my view like below:

We can change the page number display logic to below since it will accommodate for large dataset.

renderPageNumbers = pageNumbers.map(number => {
  let classes = this.state.current_page === number ? styles.active : '';

  if (number == 1 || number == this.state.total || (number >= this.state.current_page - 2 && number <= this.state.current_page + 2)) {
    return (
      <span key={number} className={classes} onClick={() => this.makeHttpRequestWithPage(number)}>{number}</span>
    );
  }
});

pagination_another_display_logic.js

Thanks for reading.

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What is JavaScript – All You Need To Know About JavaScript

What is JavaScript – All You Need To Know About JavaScript

In this article on what is JavaScript, we will learn the basic concepts of JavaScript.

After decades of improvement, JavaScript has become one of the most popular programming languages of all time. It all started in the year 1995 when Brendan Eich created JavaScript in a span of 10 days. Since then, it has seen multiple versions, updates and has grown to the next level.

Here’s a list of topics that I’ll be covering in this blog:

  1. What is JavaScript
  2. What can JavaScript do?
  3. JavaScript Frameworks
  4. The Big Picture: HTML, CSS & JavaScript
  5. Benefits of JavaScript
  6. Fundamentals of JavaScript
    VariablesConstantsData TypesObjectsArraysFunctionsConditional statementsLoopsSwitch case
What is JavaScript?

JavaScript is a high level, interpreted, programming language used to make web pages more interactive.

Have you ever thought that your website is missing something? Maybe it’s not engaging enough or it’s not as creative as you want it to be. JavaScript is that missing piece which can be used to enhance web pages, applications, etc to provide a more user-friendly experience.

What is JavaScript?

JavaScript is the language of the web, it is used to make the web look alive by adding motion to it. To be more precise, it’s a programming language that let’s you implement complex and beautiful things/design on web pages. When you notice a web page doing more than just sit there and gawk at you, you can bet that the web page is using JavaScript.

Feature of JavaScript

Scripting language and not Java: In fact, JavaScript has nothing to do with Java. Then why is it called “Java” Script? When JavaScript was first released it was called Mocha, it was later renamed to LiveScript and then to JavaScript when Netscape (founded JavaScript) and Sun did a license agreement. Object-based scripting language which supports polymorphism, encapsulation and to some extent inheritance as well.**Interpreted language: **It doesn’t have to be compiled like Java and C which require a compiler.JavaScript runs in a browser: You can run it on Google Chrome, Internet Explorer, Safari, etc. JavaScript can execute not only in the browser but also on the server and any device which has a JavaScript Engine.

What is JavaScript – Stackoverflow stats

Currently, we have 100s of programming languages and every day new languages are being created. Among these are few powerful languages that bring about big changes in the market and JavaScript is one of them.

JavaScript has always been on the list of popular programming languages. According to StackOverflow, for the 6th year in a row, JavaScript has remained the most popular and commonly used programming language.

What can JavaScript do?

JavaScript is mainly known for creating beautiful web pages & applications. An example of this is Google Maps. If you want to explore a specific map, all you have to do is click and drag with the mouse. And what sort of language could do that? You guessed it! It’s JavaScript.JavaScript can also be used in smart watches. An example of this is the popular smartwatch maker called Pebble. Pebble has created Pebble.js which is a small JavaScript Framework that allows a developer to create an application for the Pebble line of watches in JavaScript.

What is JavaScript – Applications of JavaScript
Most popular websites like Google, Facebook, Netflix, Amazon, etc make use of JavaScript to build their websites.Among things like mobile applications, digital art, web servers and server applications, JavaScript is also used to make Games. A lot of developers are building small-scale games and apps using JavaScript.## JavaScript Frameworks

One major reason for the popularity of JavaScript is the JavaScript Frameworks. Here’s a brief introduction of the most trending JavaScript frameworks :

  1. AngularJS is Google’s web development framework which provides a set of modern development and design features for rapid application development.

  2. ReactJS is another top JavaScript framework mainly maintained by Facebook and it’s behind the User Interface of Facebook and Instagram, showing off its efficiency in maintaining such high traffic applications.

What is JavaScript – JavaScript Frameworks

  1. MeteorJS is mainly used for providing back-end development. Using JavaScript on the back-end to save time and build expertise is one of the major ideas behind Meteor.

  2. jQuery can be used when you want to extend your website and make it more interactive. Companies like Google, WordPress and IBM rely on jQuery.

The Big Picture: HTML, CSS & JavaScript

Anyone familiar with JavaScript knows that it has something to do with HTML and CSS. But what is the relationship between these three? Let me explain this with an analogy.

What is JavaScript – HTML, CSS and JavaScript

Think of HTML (HyperText Markup Language) as the skeleton of the web. It is used for displaying the web.

On the other hand, CSS is like our clothes. We put on fashionable clothes to look better. Similarly, the web is quite stylish as well. It uses CSS which stands for Cascading Style Sheets for styling purpose.

Then there is JavaScript which puts life into a web page. Just like how kids move around using the skateboard, the web also motions with the help of JavaScript.

Benefits of JavaScript

There has to be a reason why so many developers love working on JavaScript. Well, there are several benefits of using JavaScript for developing web applications, here’s a few benefits:

It’s easy to learn and simple to implement. It is a weak-type programming language unlike the strong-type programming languages like Java and C++, which have strict rules for coding.

It’s all about being fast in today’s world and since JavaScript is mainly a client-side programming language, it is very fast because any code can run immediately instead of having to contact the server and wait for an answer.

Rich set of frameworks like AngularJS, ReactJS are used to build web applications and perform different tasks.

**Builds interactive websites: **We all get attracted to beautifully designed websites and JavaScript is the reason behind such attractive websites and applications.

JavaScript is an interpreted language that does not require a compiler because the web interprets JavaScript. All you need is a browser like Google Chrome or Internet Explorer and you can do all sorts of stuff in the browser.

JavaScript is platform independent and it is supported by all major browsers like Internet Explorer, Google Chrome, Mozilla Firefox, Safari, etc.

JavaScript Fundamentals

In this What is JavaScript blog, we’ll cover the following basic fundamentals of JavaScript
VariablesConstantsData TypesObjectsArraysFunctionsConditional statementsLoopsSwitch case## Variables

Variable is a name given to a memory location which acts as a container for storing data temporarily. They are nothing but reserved memory locations to store values.

What is JavaScript – Variables

To declare a variable in JavaScript use the ‘let’ keyword. For example:

let age;
age=22;

In the above example, I’ve declared a variable ‘age’ by using the ‘let’ keyword and then I’ve stored a value (22) in it. So here a memory location is assigned to the ‘age’ variable and it contains a value i.e. ’22’.

Constants

Constants are fixed values that don’t change during execution time.

To declare a constant in JavaScript use the ‘const’ keyword. For example:

const mybirthday;
mybirthday='3rd August'; 

Data types

You can assign different types of values to a variable such as a number or a string. In JavaScript, there are two categories of data types :

What is JavaScript – Data Types

Objects

An object is a standalone entity with properties and types and it is a lot like an object in real life. For example, consider a girl, whose name is Emily, age is 22 and eye-color is brown. In this example the object is the girl and her name, age and eye-color are her properties.

What is JavaScript – Objects example

Objects are variables too, but they contain many values, so instead of declaring different variables for each property, you can declare an object which stores all these properties.

To declare an object in JavaScript use the ‘let’ keyword and make sure to use curly brackets in such a way that all property-value pairs are defined within the curly brackets. For example:

let girl= {
name: 'Emily',
age: 22,
eyeColour: 'Brown'
};

In the above example, I’ve declared an object called ‘girl’ and it has 3 properties (name, age, eye colour) with values (Emily, 22, Brown).

Arrays

An array is a data structure that contains a list of elements which store multiple values in a single variable.

For example, let’s consider a scenario where you went shopping to buy art supplies. The list of items you bought can be put into an array.

What is JavaScript – Arrays example

To declare an array in JavaScript use the ‘let’ keyword with square brackets and all the array elements must be enclosed within them. For example:

let shopping=[];
shopping=['paintBrush','sprayPaint','waterColours','canvas'];

In the above example I’ve declared an array called ‘shopping’ and I’ve added four elements in it.

Also, array elements are numbered from zero. For example this is how you access the first array element:

shopping[0];		

Functions

A function is a block of organised, reusable code that is used to perform single, related action.

Let’s create a function that calculates the product of two numbers.

To declare a function in JavaScript use the ‘function’ keyword. For example:

function product(a, b) {
return a*b;
}

In the above example, I’ve declared a function called ‘product’ and I’ve passed 2 parameters to this function, ‘a’ and ‘b’ which are variables whose product is returned by this function. Now, in order to call a function and pass a value to these parameters you’ll have to follow the below syntax:

product(8,2);

In the above code snippet I’m calling the product function with a set of values (8 & 2). These are values of the variables ‘a’ and ‘b’ and they’re called as arguments to the function.

Conditional statements – if

Conditional statement is a set of rules performed if a certain condition is met. The ‘if’ statement is used to execute a block of code, only if the condition specified holds true.

What is JavaScript – if flowchart

To declare an if statement in JavaScript use the ‘if’ keyword. The syntax is:

if(condition) {
statement;
}

Now let’s look at an example:

let numbers=[1,2,1,2,3,2,3,1];
if(numbers[0]==numbers[2]) {
console.log('Correct!');
}

In the above example I’ve defined an array of numbers and then I’ve defined an if block. Within this block is a condition and a statement. The condition is ‘(numbers[0]==numbers[2])’ and the statement is ‘console.log(‘Correct!’)’. If the condition is met, only then the statement will be executed.

Conditional statements- Else if

Else statement is used to execute a block of code if the same condition is false.

What is JavaScript – Else-if flowchart

The syntax is:

if(condition) {
statement a;
}
else (condition) {
statement b;
}

Now let’s look at an example:

let numbers=[1,2,1,2,3,2,3,1];
if(numbers[0]==numbers[4] {
console.log("Correct!");
}
else {
console.log("Wrong, please try again");
}

In the above example, I’ve defined an if block as well as an else block. So if the conditions within the if block holds false then the else block gets executed. Try this for yourself and see what you get!

**Loops **

Loops are used to repeat a specific block until some end condition is met. There are three categories of loops in JavaScript :

  1. while loop
  2. do while loop
  3. for loop
While loop

While the condition is true, the code within the loop is executed.

What is JavaScript – while loop flowchart

The syntax is:

while(condition) {
loop code;
}

Now let’s look at an example:

let i=0;
while(i < 5) {
console.log("The number is " +i);
i++;
}

In the above example, I’ve defined a while loop wherein I’ve set a condition. As long as the condition holds true, the while loop is executed. Try this for yourself and see what you get!

Do while loop

This loop will first execute the code, then check the condition and while the condition holds true, execute repeatedly.

What is JavaScript – Do while loop flowchart

Refer the syntax to better understand it:

do {
loop code;
} while(condition);

This loop executes the code block once before checking if the condition is true, then it will repeat the loop as long as the condition holds true.

Now let’s look at an example:

do {
console.log("The number is " +i);
i++;
}
while(i > 5);

The above code is similar to the while loop code except, the code block within the do loop is first executed and only then the condition within the while loop is checked. If the condition holds true then the do loop is executed again.

For loop

The for loop repeatedly executes the loop code while a given condition is TRUE. It tests the condition before executing the loop body.

What is JavaScript – for loop flowchart

The syntax is:

for(begin; condition; step) {
loop code;
}

In the above syntax:

  • begin statement is executed one time before the execution of the loop code
  • condition defines the condition for executing the loop code
  • step statement is executed every time after the code block has been executed

For example:

for (i=0;i<5;i++) {
console.log("The number is " +i);
}

In the above example, I’ve defined a for loop within which I’ve defined the begin, condition and step statements. The begin statement is that ‘i=0’. After executing the begin statement the code within the for loop is executed one time. Next, the condition is checked, if ‘i<5’ then, the code within the loop is executed. After this, the last step statement (i++) is executed. Try this and see what you get!

Switch Case

The switch statement is used to perform different actions based on different conditions.

What is JavaScript – Switch case flowchart

Let’s look at the syntax for switch case:

switch(expression) {
case 1:
code block 1
break;
case 2:
code block 2
break;
default:
code block 3
break;
}

How does it work?

  • Switch expression gets evaluated once
  • Value of the expression is compared with the values of each case
  • If there is a match, the associated block of code is executed

Let’s try this with an example:

let games='football';
switch(games) {
case "throwball":
console.log("I dislike throwball!");
break;
case "football":
console.log("I love football!");
break;
case "cricket":
console.log("I'm a huge cricket fan!");
break;
default:
console.log("I like other games");
break;
}

In the above example the switch expression is ‘games’ and the value of games is ‘football’. The value of ‘games’ is compared with the value of each case. In this example it is compared to ‘throwball’, ‘cricket’ and ‘football’. The value of ‘games’ matches with the case ‘football’, therefore the code within the ‘football’ case is executed. Try this for yourself and see what you get!

With this, we come to the end of this blog. I hope you found this blog informative and I hope you have a basic understanding of JavaScript. In my next blog on JavaScript I’ll be covering in-depth concepts, so stay tuned.

Also, check out our video on JavaScript Fundamentals if you want to get started as soon as possible and don’t forget to leave a comment if you have any doubt and also, let us know whether you’d want us to create more content on JavaScript. We are listening!