Building a Calculator with React Hooks

Building a Calculator with React Hooks

If you are like me, when you first heard of React Hooks you were maybe a little bit ambivalent or confused by what all the hype was about

What’s the big deal if I don’t have to write out class components anymore? However once you dive in and get to using them, I can’t really see myself going back to my pre-Hook days. In the immortal words of Blues Traveller, “The hook brings you back. I ain’t tellin’ you no lie.”

For a while, I was looking for a guide about how to use Hooks in connection with the Context API. After only finding a few examples out there that explained the concept fully, I decided to do what any good developer should do; pore over the docs and build something myself. Struggling through it and learning it on your own is one of the best ways to absorb knowledge. This is a guide for how to build the same project that I did with the use of Hooks and Context.

This project is going to be a basic calculator app similar to the iPhone calculator. Since this is just a simple desktop app I have replaced the % button with a back button. Though I wouldn’t use this to take the SATs, you could definitely add up the number of toes you have on it.

There is a working deployed version of the project, or you can view all of the code on GitHub.

To get started we are just going to use create-react-app. You can get started by running the following:

npx create-react-app calculatorcd calculatornpm start

The file structure of the app should look like the following. In the src folder create the following files or just leave the App.js and index.js.

src
├── App.js
├── index.js
└── components
    ├── BackButton.js
    ├── Calculator.js
    ├── ClearButton.js
    ├── Display.js    
    ├── EqualButton.js
    ├── FunctionButton.js
    ├── NegativeButton.js
    ├── NumberButton.js
    ├── NumberProvider.js
    └── styles
        └── Styles.js

If you want to follow along exactly you can also install Styled Components for the CSS.

npm -i styled-components

You can then add the Styled CSS from this link to the Styles.js file or add your own.

The Calculator.js file should setup the display and number pad. It should contain all of the button types.

import React from 'react';
import NumberButton from './NumberButton';
import FunctionButton from './FunctionButton';
import ClearButton from './ClearButton';
import Display from './Display';
import EqualButton from './EqualButton';
import BackButton from './BackButton';
import NegativeButton from './NegativeButton';
import { CalculatorStyles } from './styles/Styles';

const Calculator = () => (
  <CalculatorStyles>
    <div className="display">
      <h1>CALC-U-LATER</h1>
      <Display />
    </div>
    <div className="number-pad">
      <ClearButton />
      <BackButton />
      <NegativeButton />
      <FunctionButton buttonValue="/" />
      <NumberButton buttonValue={7} />
      <NumberButton buttonValue={8} />
      <NumberButton buttonValue={9} />
      <FunctionButton buttonValue="*" />
      <NumberButton buttonValue={4} />
      <NumberButton buttonValue={5} />
      <NumberButton buttonValue={6} />
      <FunctionButton buttonValue="-" />
      <NumberButton buttonValue={1} />
      <NumberButton buttonValue={2} />
      <NumberButton buttonValue={3} />
      <FunctionButton buttonValue="+" />
      <div className="zero-button">
        <NumberButton buttonValue={0} />
      </div>
      <NumberButton buttonValue="." />
      <EqualButton />
    </div>
  </CalculatorStyles>
);

export default Calculator;

Caclulator.js

You will notice that all of the button components are added in here along with the number display. Each of the button components are essentially the same. They should all follow the same basic structure. The zero-button gets a separate div since we are using CSS Grid for the layout and it needs to span two columns. (PS — If you want to know more about CSS Grid I did a little article on the basics.)

You may notice that the buttonValue props is only needed for the NumberButton and FunctionButton components. Each of the buttons should follow the same basic structure with a unique name. You can reference the file structure up above to see which buttons are needed. The buttons should have the symbol written in the button component if they are not passed a buttonValue via props. Create one of these for each of the button types in your file structure.

import React from 'react';

const ButtonName = ({ buttonValue }) => {
  return (
    <button type="button">{buttonValue}</button>
  );
};

export default ButtonName;

BasicButton.js

After this you should have the basic structure of a calculator. We are going to come back to the display in just a bit. Now we are going to get into the inner workings of the app and see how we can use our Hooks and Context.

We are now going to create the NumberProvider.js . This is the heart of your app and where our functions are going to live. If you have never used the React Context API it is a great tool to help pass data from one component to another.

Think of when you have components that are nested within each other. In the past you would have to “prop drill” . This is when you pass the data or function through as props in down through nested components. This is hardly ideal, especially when you start to go several layers deep.

However, with this provider component, it allows you to pass data to any nested component, no matter how deep. This number provider will wrap our App component. Now whenever we want to get data, or use a function that lives in the provider, it is globally available. This gets us out of having to “prop drill” through nested components. You maintain the single source of truth that is the essence of React. To get started you need to create the provider. It should look like the folowing:

import React from 'react';

export const NumberContext = React.createContext();

const NumberProvider = props => {
  const number = "0"
  return (
    <NumberContext.Provider
      value={{
        number
      }}
    >
      {props.children}
    </NumberContext.Provider>
  );
};

export default NumberProvider;

BasicProvider.js

The basic provider is created and any value that is passed in is now available to all nested components. In order to make this available we are going to wrap our App component so it is globally available. Our App will have this code.

import React from 'react';
import Calculator from './components/Calculator';
import NumberProvider from './components/NumberProvider';

const App = () => (
  <NumberProvider>
    <Calculator />
  </NumberProvider>
);

export default App;

App.js

Now we can add in the code for our display. We can display the value by passing in the useContext function from the new React Hooks API. We no longer have to pass in prop through nested components. The display should look like:

import React, { useContext } from 'react';
import { NumberContext } from './NumberProvider';
import { DisplayStyles } from './styles/Styles';

const Display = () => {
  const { number } = useContext(NumberContext);
  return (
    <DisplayStyles>
      <h2>{number}</h2>
      <p>Enter Some Numbers</p>
    </DisplayStyles>
  );
};

export default Display;

Display.js

The number that you passed three levels up in the NumberProvider is immediately available to the Display component by calling useContext and passing our created NumberContext. Your number display is now up and running as it is showing number which we have set to zero.

Now of course our calculator is showing a single zero. This is great if you are counting the number of hours of sleep I get with a new born son, but not so great if trying to add anything else, so let’s use some hooks going get this calculator calculating.

If you haven’t used a hook before, it essentially allows you to get rid of the class syntax, and instead have state within functional components. Here we can add the following to our NumberProvider.js file in order to create our first hook.

import React, { useState } from 'react';

export const NumberContext = React.createContext();

const NumberProvider = props => {
  const [number, setNumber] = useState('');

  const handleSetDisplayValue = num => {
    if (!number.includes('.') || num !== '.') {
      setNumber(`${(number + num).replace(/^0+/, '')}`);
    }
  };

  return (
    <NumberContext.Provider
      value={{
        handleSetDisplayValue,
        number
      }}
    >
      {props.children}
    </NumberContext.Provider>
  );
};

export default NumberProvider;

NumberProvider.js

There might be some syntax you have not seen. Rather than writing out our class with state we break each part of state into its own smaller number variable. There is also setNumber which acts the same as setState function, but now works for a specific variable, and can be called when necessary. useState allows us to set an initial value.

We are now able to use this all in our function to pass the number button values into the display. In this app the calculator is using strings to get the input. There are checks to make sure that you can not have multiple . in your number and that you do not have series of zeroes to start your number.

Now you can call this function using the Context API in any of the nested components.

import React, { useContext } from 'react';
import { NumberContext } from './NumberProvider';

const NumberButton = ({ buttonValue }) => {
  const { handleSetDisplayValue } = useContext(NumberContext);
  return (
    <button type="button" onClick={() => handleSetDisplayValue(buttonValue)}>
      {buttonValue}
    </button>
  );
};

export default NumberButton;

NumberButton.js

Now you have working string of numbers maker. You can see how you can start to inject the values that you set in the NumberProvider into the other components of the app via the useContext function. State and the functions that affect it are held in the NumberProvider . You just have to call in the specific context that you want. You can start to see how this would be great as you start to add more complexity to your app. Say you want a user component to check that you are logged in to use special features. You can create a separate provider that holds the user data and makes that available any nested component.

We can continue to add in functions to our calculator and pass them to the proper component through the useContext function that is built in.

The completed NumberProvider is found below and contains the following functions that are used with hooks.

  • handleSetDisplayValue sets the value that you are typing into the display. We are checking that it there is only one decimal in the number string and we are limiting the number length to 8 characters. Think of this as more a tip calculator than one to get you through your calculus exam. It takes in the buttonValue property in NumberButton.js .
  • handleSetStoredValue takes our display string and stores it so that we can enter another number. This is our stored value. It will be used as a helper function.
  • handleClearValue resets everything back to 0. This is your clear function. It will get passed to ClearButton.js.
  • handleBackButton allows you to delete your previously entered characters one at a time until you get back to 0. This belongs in the BackButton.js file.
  • handleSetCalcFunction is where you get your math function. It sets if you are adding, subtracting, dividing, or multiplying. It gets passed into the FunctionButton.js file and takes in the buttonValue property.
  • handleToggleNegative does just as the name implies. It allows you do so for either the display value or a stored value after a calculation. This of course goes in NegativeButton.js.
  • doMath does the Math. Finally. Since this is only a simple four function calculator it is just using simple switch function depending upon the functionType that we have in state. We are using parseInt since we are passing our number in as strings. Also we are rounding to only three decimal places, to make sure that we do not have crazy long numbers.
import React, { useState } from 'react';

export const NumberContext = React.createContext();

const NumberProvider = props => {
  const [number, setNumber] = useState('');
  const [storedNumber, setStoredNumber] = useState('');
  const [functionType, setFunctionType] = useState('');

  const handleSetDisplayValue = num => {
    if ((!number.includes('.') || num !== '.') && number.length < 8) {
      setNumber(`${(number + num).replace(/^0+/, '')}`);
    }
  };

  const handleSetStoredValue = () => {
    setStoredNumber(number);
    setNumber('');
  };

  const handleClearValue = () => {
    setNumber('');
    setStoredNumber('');
    setFunctionType('');
  };

  const handleBackButton = () => {
    if (number !== '') {
      const deletedNumber = number.slice(0, number.length - 1);
      setNumber(deletedNumber);
    }
  };

  const handleSetCalcFunction = type => {
    if (number) {
      setFunctionType(type);
      handleSetStoredValue();
    }
    if (storedNumber) {
      setFunctionType(type);
    }
  };

  const handleToggleNegative = () => {
    if (number) {
      if (number > 0) {
        setNumber(`-${number}`);
      } else {
        const positiveNumber = number.slice(1);
        setNumber(positiveNumber);
      }
    } else if (storedNumber > 0) {
      setStoredNumber(`-${storedNumber}`);
    } else {
      const positiveNumber = storedNumber.slice(1);
      setStoredNumber(positiveNumber);
    }
  };

  const doMath = () => {
    if (number && storedNumber) {
      switch (functionType) {
        case '+':
          setStoredNumber(`${Math.round(`${(parseFloat(storedNumber) + parseFloat(number)) * 100}`) / 100}`);
          break;
        case '-':
          setStoredNumber(`${Math.round(`${(parseFloat(storedNumber) - parseFloat(number)) * 1000}`) / 1000}`);
          break;
        case '/':
          setStoredNumber(`${Math.round(`${(parseFloat(storedNumber) / parseFloat(number)) * 1000}`) / 1000}`);
          break;
        case '*':
          setStoredNumber(`${Math.round(`${parseFloat(storedNumber) * parseFloat(number) * 1000}`) / 1000}`);
          break;
        default:
          break;
      }
      setNumber('');
    }
  };

  return (
    <NumberContext.Provider
      value={{
        doMath,
        functionType,
        handleBackButton,
        handleClearValue,
        handleSetCalcFunction,
        handleSetDisplayValue,
        handleSetStoredValue,
        handleToggleNegative,
        number,
        storedNumber,
        setNumber,
      }}
    >
      {props.children}
    </NumberContext.Provider>
  );
};

export default NumberProvider;

NumberProvider.js

You will also need a display. In this case it will show the number and the storedNumber along with your functionType. There are a few check such as showing a 0 when you have an empty string as a number.

import React, { useContext } from 'react';
import { NumberContext } from './NumberProvider';
import { DisplayStyles } from './styles/Styles';

const Display = () => {
  const { number, storedNumber, functionType } = useContext(NumberContext);
  return (
    <DisplayStyles>
      <h2>{!number.length && !storedNumber ? '0' : number || storedNumber}</h2>
      <p>{!storedNumber ? 'ENTER SOME NUMBERS' : `${storedNumber} ${functionType} ${number}`}</p>
    </DisplayStyles>
  );
};

export default Display;

Display.js

For brevity sake I am not going to include all of the button functions since they are pretty much the same as the NumberButton.js file above. Just be sure that you pass in a buttonValue prop when necessary, and that you are passing in the correct function from the above list.

If you would like to see the entire code it can be found over in this

GitHub Repo

Calc-U-Later Deploy

I hope that this clears up a bit about how React Hooks and the Context API can be used together. Using these built in React features offers several benefits.

  • handleSetDisplayValue sets the value that you are typing into the display. We are checking that it there is only one decimal in the number string and we are limiting the number length to 8 characters. Think of this as more a tip calculator than one to get you through your calculus exam. It takes in the buttonValue property in NumberButton.js .
  • handleSetStoredValue takes our display string and stores it so that we can enter another number. This is our stored value. It will be used as a helper function.
  • handleClearValue resets everything back to 0. This is your clear function. It will get passed to ClearButton.js.
  • handleBackButton allows you to delete your previously entered characters one at a time until you get back to 0. This belongs in the BackButton.js file.
  • handleSetCalcFunction is where you get your math function. It sets if you are adding, subtracting, dividing, or multiplying. It gets passed into the FunctionButton.js file and takes in the buttonValue property.
  • handleToggleNegative does just as the name implies. It allows you do so for either the display value or a stored value after a calculation. This of course goes in NegativeButton.js.
  • doMath does the Math. Finally. Since this is only a simple four function calculator it is just using simple switch function depending upon the functionType that we have in state. We are using parseInt since we are passing our number in as strings. Also we are rounding to only three decimal places, to make sure that we do not have crazy long numbers.

Please let me know your thoughts or if there are any issues that you come across in the code. Hopefully this shined a bit of life onto something that you may not have been familiar with before.

Check out more of my work at https://theran.co.

Recommended Courses:

The Complete Web Development Tutorial Using React and Redux

React Hooks

React From The Ground Up

React for visual learners

Hello React - React Training for JavaScript Beginners

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

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

Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on Facebook | Twitter

Learn More

☞ Understanding TypeScript

☞ Typescript Masterclass & FREE E-Book

☞ React - The Complete Guide (incl Hooks, React Router, Redux)

☞ Modern React with Redux [2019 Update]

☞ The Complete React Developer Course (w/ Hooks and Redux)

☞ React JS Web Development - The Essentials Bootcamp

☞ React JS, Angular & Vue JS - Quickstart & Comparison

☞ The Complete React Js & Redux Course - Build Modern Web Apps

☞ React JS and Redux Bootcamp - Master React Web Development