useReducer vs useState in React

useReducer vs useState in React

This tutorial doesn’t explain both React hooks in detail, but explains their different use case scenarios. There are many people who ask me whether to use useState or useReducer; that’s why I thought getting together all my thoughts in one article is the best thing to deal with it.

This tutorial doesn’t explain both React hooks in detail, but explains their different use case scenarios. There are many people who ask me whether to use useState or useReducer; that’s why I thought getting together all my thoughts in one article is the best thing to deal with it.

Since React Hooks have been released, function components in React can use state and side-effects. There are two main hooks that are used for modern state management in React: useState and useReducer.

Table of Contents
  • When to use useState or useReducer?
  • Simple vs. Complex State with Hooks
  • Simple vs. Complex State Transitions with Hooks
  • Multiple State Transitions operate on one State Object
  • State Changes and their Logic
  • State Changes and the Trigger
When to use useState or useReducer?

Everyone starting out with React Hooks gets to know pretty soon the useState hook. It’s there to update state in React function components by offering to set the initial state and returning the actual state and an updater function:

import React, { useState } from 'react';

const Counter = () => {
  const [count, setCount] = useState(0);

  const handleIncrease = () => {
    setCount(count => count + 1);
  };

  const handleDecrease = () => {
    setCount(count => count - 1);
  };

  return (
    <div>
      <h1>Counter with useState</h1>
      <p>Count: {count}</p>

      <div>
        <button type="button" onClick={handleIncrease}>
          +
        </button>
        <button type="button" onClick={handleDecrease}>
          -
        </button>
      </div>
    </div>
  );
};

export default Counter;

In contrast, the useReducer hook can be used to update state as well, but it happens in a more sophisticated way with a given reducer function and an initial state which returns the actual state and a dispatch function to alter the state in an implicit way by mapping actions to state transitions:

import React, { useReducer } from 'react';

const counterReducer = (state, action) => {
  switch (action.type) {
    case 'INCREASE':
      return { ...state, count: state.count + 1 };
    case 'DECREASE':
      return { ...state, count: state.count - 1 };
    default:
      throw new Error();
  }
};

const Counter = () => {
  const [state, dispatch] = useReducer(counterReducer, { count: 0 });

  const handleIncrease = () => {
    dispatch({ type: 'INCREASE' });
  };

  const handleDecrease = () => {
    dispatch({ type: 'DECREASE' });
  };

  return (
    <div>
      <h1>Counter with useReducer</h1>
      <p>Count: {state.count}</p>

      <div>
        <button type="button" onClick={handleIncrease}>
          +
        </button>
        <button type="button" onClick={handleDecrease}>
          -
        </button>
      </div>
    </div>
  );
};

export default Counter;

Even though both components use different React Hooks for the state management, they solve the same business case. So when would you use which state management solution? Let’s dive into it …

Simple vs. Complex State with Hooks

The previous reducer example already encapsulated the count property into a state object. We could have done it simpler by using the count as the actual state. Refactoring the code to not having a state object, but only the count integer as JavaScript primitive, we can already see that the use case doesn’t have a complex state to manage:

import React, { useReducer } from 'react';

const counterReducer = (state, action) => {
  switch (action.type) {
    case 'INCREASE':
      return state + 1;
    case 'DECREASE':
      return state - 1;
    default:
      throw new Error();
  }
};

const Counter = () => {
  const [count, dispatch] = useReducer(counterReducer, 0);

  const handleIncrease = () => {
    dispatch({ type: 'INCREASE' });
  };

  const handleDecrease = () => {
    dispatch({ type: 'DECREASE' });
  };

  return (
    <div>
      <h1>Counter with useReducer</h1>
      <p>Count: {count}</p>

      <div>
        <button type="button" onClick={handleIncrease}>
          +
        </button>
        <button type="button" onClick={handleDecrease}>
          -
        </button>
      </div>
    </div>
  );
};

export default Counter;

The example shows that we may be better off with a simpler useState hook here, because there is no complex state object involved. We could refactor our state object to a primitive.

Anyway, I would argue once you move past managing a primitive (e.g. string, integer, boolean) but rather a complex object (e.g. with arrays and additional primitives), you may be better of using useReducer to manage this object. Perhaps a good rule of thumb:

  • Use useState whenever you manage a JS primitive (e.g. string, boolean, integer).
  • Use useReducer whenever you manage an object or array.

The rule of thumb suggests, for instance, once you spot const [state, setState] = useState({ firstname: 'Robin', lastname: 'Wieruch' }) in your code, you may be better off with useReducer instead of useState.

Simple vs. Complex State Transitions with Hooks

We didn’t use by chance two different action types (INCREASE and DECREASE) for our previous state transitions. What could we have done differently? By using the optional payload that can be used within every dispatched action object, we could say from the outside by how much we want to increase or decrease the count; moving the state transition towards being more implicit:

import React, { useReducer } from 'react';

const counterReducer = (state, action) => {
  switch (action.type) {
    case 'INCREASE_OR_DECREASE_BY':
      return state + action.by;
    default:
      throw new Error();
  }
};

const Counter = () => {
  const [count, dispatch] = useReducer(counterReducer, 0);

  const handleIncrease = () => {
    dispatch({ type: 'INCREASE_OR_DECREASE_BY', by: 1 });
  };

  const handleDecrease = () => {
    dispatch({ type: 'INCREASE_OR_DECREASE_BY', by: -1 });
  };

  return (
    <div>
      <h1>Counter with useReducer</h1>
      <p>Count: {count}</p>

      <div>
        <button type="button" onClick={handleIncrease}>
          +
        </button>
        <button type="button" onClick={handleDecrease}>
          -
        </button>
      </div>
    </div>
  );
};

export default Counter;

But we didn’t. That’s one important lesson when using reducers: Always try to be explicit with your state transitions. The latter example with only one state transitions tries to put every logic into one block, but that’s not very much desired when using a reducer function. Rather we want to be able to reason effortless about our state transitions. By having two state transitions instead, as before in our code, we can always reason about it by just reading the action type’s name.

Using useReducer over useState gives us predictable state transitions. It comes in very powerful when your state changes become more complex and you want to have one place – the reducer function – to reason about them. The reducer functions encapsulates this logic perfectly.

A rule of thumb may suggest: Once you spot multiple setState() calls in succession, try to encapsulate these things in one reducer function to dispatch only one action instead.

A great side-effect of having all state in one object is the possibility to use the browser’s local storage for it. That’s how you could always cache a slice of your state with local storage and retrieve it as initial state for useReducer whenever you restart your application.

Multiple State Transitions operate on one State Object

Once your application grows in size, you will most likely deal with more complex state and state transitions. That’s what we went through in the last two sections of this tutorial. However, one thing to notice is that the state object didn’t just grew in complexity, but also in size of operations that are performed on this object.

Take for instance the following reducer that operates on one state object with multiple state transitions:

const todoReducer = (state, action) => {
  switch (action.type) {
    case 'DO_TODO':
      return state.map(todo => {
        if (todo.id === action.id) {
          return { ...todo, complete: true };
        } else {
          return todo;
        }
      });
    case 'UNDO_TODO':
      return state.map(todo => {
        if (todo.id === action.id) {
          return { ...todo, complete: false };
        } else {
          return todo;
        }
      });
    case 'ADD_TODO':
      return state.concat({
        task: action.task,
        id: action.id,
        complete: false,
      });
    default:
      throw new Error();
  }
};

It only makes sense to keep everything in one state object (e.g. list of todo items) while operating with multiple state transitions on it. It would be less predictable and maintainable implementing the same business logic with useState instead.

Often you will start out with useState but refactor your state management to useReducer, because the state object becomes more complex or the number of state transitions add up over time. However, there are other cases as well where it makes sense to group different properties, that don’t belong together on first glance, in one state object. For instance, this tutorial that showcases how to fetch data with useEffect, useState, and useReducer groups properties that are dependent on each other together in one state object:

const [state, dispatch] = useReducer(dataFetchReducer, {
  isLoading: false,
  isError: false,
  data: initialData,
});

One could argue that the isLoading and isError properties could be managed separately in two useState hooks, but when looking at the reducer function, one can see that it’s best to put them together in one state object because they conditionally dependent on each other:

const dataFetchReducer = (state, action) => {
  switch (action.type) {
    case 'FETCH_INIT':
      return {
        ...state,
        isLoading: true,
        isError: false
      };
    case 'FETCH_SUCCESS':
      return {
        ...state,
        isLoading: false,
        isError: false,
        data: action.payload,
      };
    case 'FETCH_FAILURE':
      return {
        ...state,
        isLoading: false,
        isError: true,
      };
    default:
      throw new Error();
  }
};

After all, not only the state object complexity or the number of state transitions is important, but also how properties fit together in context to be managed in one state object. If everything is managed at different places with useState, it becomes harder to reason about the whole thing as one unit. Another important point is the improved developer experience: Since you have this one place with one state object and multiple transitions, it’s far easier to debug your code if anything goes wrong.

A great side-effect of having all state transitions neatly in one reducer function is the ability to export the reducer for unit tests. It’s simpler to reason about a state object with multiple state transitions if you just need to test all state transitions by having only one function: (state, action) => newState. You can test all state transitions by providing all available action types and various matching payloads.

Logic for State Changes

There is a difference of where the logic for state transitions is placed when using useState or useReducer. As we have seen for the previous useReducer examples, the logic for the state transitions happens within the reducer function. The action only comes with the minimum information to perform the transition based on the current state: (state, action) => newState. This comes especially handy if you rely on the current state to update your state.

const todoReducer = (state, action) => {
  switch (action.type) {
    case 'DO_TODO':
      return state.map(todo => {
        if (todo.id === action.id) {
          return { ...todo, complete: true };
        } else {
          return todo;
        }
      });
    case 'UNDO_TODO':
      return state.map(todo => {
        if (todo.id === action.id) {
          return { ...todo, complete: false };
        } else {
          return todo;
        }
      });
    case 'ADD_TODO':
      return state.concat({
        task: action.task,
        id: action.id,
        complete: false,
      });
    default:
      throw new Error();
  }
};

Everything your React component cares about is dispatching the action:

import uuid from 'uuid/v4';

// Somewhere in your React components ...

const handleSubmit = event => {
  dispatch({ type: 'ADD_TODO', task, id: uuid() });
};

const handleChange = () => {
  dispatch({
    type: todo.complete ? 'UNDO_TODO' : 'DO_TODO',
    id: todo.id,
  });
};

Now imagine you would perform the same state transitions but with useState instead. There is no pre-defined entity like the reducer where all business logic is situated. There is no clear separation – as far as you don’t extract the logic into separate functions – and all your state relevant logic ends up in your handlers which call the state updater functions from useState eventually. Over time, it becomes harder to separate state logic from view logic and the components grow in complexity. Reducers instead offer the perfect place for logic that alters the state.

Trigger of the State Change

The vertical component tree in React becomes deeper once you grow your application. If the state is simple and belongs co-located (state + state trigger) to a component (e.g. search input field which is made a controlled component), using useState may be the perfect fit. The state is encapsulated within this one component:

import React, { useState } from 'react';

const App = () => {
  const [value, setValue] = useState('Hello React');

  const handleChange = event => setValue(event.target.value);

  return (
    <div>
      <label>
        My Input:
        <input type="text" value={value} onChange={handleChange} />
      </label>

      <p>
        <strong>Output:</strong> {value}
      </p>
    </div>
  );
};

export default App;

However, sometimes you want to manage state at a top-level but trigger the state changes somewhere deep down in your component tree. It’s possible to pass both the updater function from useState or the dispatch function from useReducer via props down the component tree, but using React’s context API may be a valid alternative to avoid the prop drilling (passing props trough each component level). Then having one dispatch function that is used with different action types and payloads may be the better option than using multiple updater functions from useState that need to be passed down individually. The dispatch function can be passed down once with React’s useContext hook. A good example how this works can be seen in this state management tutorial for React using useContext.

The decision whether to use useState or useReducer isn’t always black and white. There are many shades of grey in between. However, I hope the article gave you a few key understandings on when to use useState or useReducer. Here you can find a GitHub repository with a few examples. The following facts give you a summarized overview, however they only reflect my opinion on this topic:

Use useState if:

  • A) if you manage JavaScript primitives as state
  • B) if you have simple state transitions
  • C) if you want to have business logic within your component
  • D) if you have different properties that don’t change in any correlated manner and can be managed by multiple useState hooks
  • E) if your state is co-located to your component
  • F) if you’ve got a small application (but the lines are blurry here)

Use useReducer if:

  • A) if you manage JavaScript objects or arrays as state
  • B) if you have complex state transitions
  • C) if you want to move business logic into reducers
  • D) if you have different properties that are tied together and should be managed in one state object
  • E) if you want to update state deep down in your component tree
  • F) if you’ve got a medium size application (but the lines are blurry here)
  • G) if you want have an easier time testing it
  • H) if you want a more predictable and maintainable state architecture

Note: Check out when to use useReducer or Redux if you are interested in a comparison.

If you want to go through a more comprehensive example where useState and useReducer are used together, check out this extensive walkthrough for modern state management in React. It almost mimics Redux by using useContext for “global” state management where it’s possible to pass down the dispatch function once.

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.

URLs and Webpack in Reactjs

URLs and Webpack in Reactjs

URLs and Webpack in Reactjs - I am still a newbie in ReactJS. I've been following series of tutorials and articles on the framework and decided to start putting what I've learnt so far into practice.

My website, dillionmegida.com was built with PHP. You could check it out as I highly appreciate reviews. I'm though aspiring to be a full-stack javascript developer so I'm in some way trying to depart from PHP :)

I decided to replicate my homepage using React and to broaden my skills in using components.

It was going quite successful until I tried using an <img> JSX element. I used it like;

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src='../img/deee.jpeg' alt='My profile picture'/>
    </div>
)
export default Profilepic;

The img folder was a sub-directory of the src folder.

My aim here was to have my profile picture as a component with some styling to be used on my homepage and any other desired page. The src for the img tag was not been used appropriately as my image was not displayed.

I paused to think of the problem, inspected my page and discovered the src displayed there was exactly as I inputted it. So silly of me :( I made some researches which helped me remember that most attributes of JSX element are not as mostly used with HTML, but have to be enclosed in curly braces.

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={'../img/deee.jpeg'} alt='My profile picture'/>
    </div>
)
export default Profilepic;

I tried rendering the page again and my image was still not displayed.

Funny enough, I quickly thought of a trick (for the first time);

...
import Dp from '../img/deee.jpeg'
...
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={Dp} alt='My profile picture'/>
    </div>
)

To my amazement, it worked. I was excited and at the same time sad, with feeling of little guilt. I didn't know why. lol. I said to myself, 'I am not doing the right thing :(' and also asked myself, 'Is react as crazy as this?'

I headed back to google to make some more research and got to discover that the webpack that React (create-react-app) automatically installed had been configured to use the public folder (at the same level with src folder) for relative URLs (such as my image URL).

Using ...<img src={'../img/deee.jpeg'} />..., React was actually checking the public folder for the image sub-directory which it couldn't find.

Solution

1. Change the location of the image folder

I changed the location of the image folder making it a sub-directory under the public directory and it worked as expected.

2. Use the require keyword

Just as the import keyword is used for relative URLs, the require keyword does same. So, I was able to do this;

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={require('../img/deee.jpeg')} alt='My profile picture'/>
    </div>
)
export default Profilepic;

and in the other pages where the Profilepic component was required and used, my image displayed perfectly. :D

Like I said, I am still a newbie at ReactJS but I hope this little experience would be helpful for you too. There are other super powers of webpacks too which I would still be learning. Please do share in the comment section corrections on this article and also helpful Tips.

I'll be documenting my experience in my ReactJS journey as much as I can. Stay tuned and thanks for reading.

Originally published by Megida Dillion at dillion.hashnode.dev

=======================================================

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