Deploy Containers Close to Your Users

This Engineering Education (EngEd) Program is supported by Section.

Instantly deploy containers globally. Section is affordable, simple and powerful.

Get Started for Free.

Building a currency converter using Fixer.io react and material-UI

December 17, 2021

A currency converter is an application that displays the equivalent value represented by the different currencies in the world. This article will give the reader a step-by-step guide on building a currency converting application with React and styling its components with Material UI.

Prerequisites for this article

  • A text editor, e.g., VSCode.
  • A good understanding of HTML, CSS, and JavaScript programming language.
  • A working installation of Node.js.

Creating the React app

Head to the project folder and run the command below to create a new React application.

npx create-react-app project-name

After creating the new React application, open a text editor and clear the default code in App.js and App.css in readiness to integrate Material UI into your application. To open the application locally in a browser, run:

npm start

Getting started with Material UI

Material UI is a component-based CSS framework that helps developers build React applications by providing several relevant components for different parts of your project.

MUI components work separately. They are self-supporting and will only display the styles they need to show. Therefore, they do not depend on worldwide style-sheets like normalize.css.

You require the @material-ui/core, which can easily be installed with npm or yarn. If you wish to use icons, you can also include the @material-ui/icons package.

Here is the command to install these packages in your app as dependencies:

npm install @material-ui/core @material-ui/icons

Now, you can find the Material UI in your app’s package.json file like in the image below:

package-json

To use any of the Material UI components in your application, head to the MUI official docs components page. Then, you can utilize any of the components as illustrated in the documentation.

It’s ideal to refer to each component’s demo page to see how they should be imported. Below is a code sample that will show you all you need to use MUI in your application:

import * as React from 'react';
import ReactDOM from 'react-dom';
import Button from '@mui/material/Button';

function App() {
  return <Button variant="contained">Hello World</Button>;
}

ReactDOM.render(<App />, document.querySelector('#app'));

Building the currency converter

This app will have “dollar icons” from Material UI, a header, two inputs for the currencies you are comparing, and two select components that you will use to choose the currencies.

This app will use fixer.io API to fetch the latest currency rates. So, if you change the values in one currency, the equivalent value for another set currency will be automatically displayed.

To get started, create a new file and name it CurrencyInput.js. Create a CurrencyInput function and pass in props as an argument. Then, create two input and select elements. Pass in props.amount and props.currency as values in the input and select tags respectively.

Next, set a map function that will iterate through the option tag in the select tag, which we will call currency, and set its value to currency.

The next thing to do is to define the propTypes. propTypes in React are a mechanism that makes sure that components use the right data sort and pass the correct data, and that components use the right type of props and that receiving components get the correct type of props. To do that, first, run the command below in your terminal:

yarn add prop-types

Next, import and call the required propsTypes for this application, amount as number, currency as a string, and currencies as an array. Lastly, export the CurrentInput function. Here is the code for the procedure:

import React from 'react'
import propTypes from "prop-types"

const CurrencyInput = (props) => {
    return (
        <div className="currency-input">
            <input type="text" value={props.amount} onChange={event => props.onAmountChange(event.target.value)}  />
            <select value={props.currency} onChange ={event => props.onCurrencyChange(event.target.value)}>
                {props.currencies.map((currency => (
                    <option value={currency}>{currency}</option>
                )))}
                </select>   
        </div>
    )
}

CurrencyInput.propTypes = {
    amount: propTypes.number.isRequired,
    currency: propTypes.string.isRequired,
    currencies: propTypes.array,
    onAmountChange: propTypes.func,
    onCurrencyChange: propTypes.func
}

export default CurrencyInput

Creating states for the app components

Head to the App.js file and create a new App function. Next, create four states that will control the state of the two inputs and two currency components in the app using the hook useState.

Next, import the CurrencyInput component and call it twice in the App function to represent the input and select for two currencies and call the states you created in their relevant input tags.

import CurrencyInput from "./CurrencyInput";
import { useState } from "react";

function App() {
  const [amount1, setAmount1] = useState(1);
  const [amount2, setAmount2] = useState(1);
  const [currency1, setCurrency1] = useState('USD');
  const [currency2, setCurrency2] = useState('EUR');

  return (
<div>
  <CurrencyInput
        amount={amount1}
        currency={currency1} />
      <CurrencyInput
        amount={amount2}
        currency={currency2} />
</div>
  );
}

Using fixer.io to get Real Currency Data

Head to the Fixer official site and click on “GET YOUR FREE API KEY” if you do not already have an account with them. Next, navigate to the free plan, which will direct you to a Signup page where you will be required to fill in your correct credentials.

After signing in, you will be redirected to a page to see your API access keys and endpoints. Copy the endpoint data. Your application will need to get the latest currency rates with another react hook called useEffect.

To do that, first, run yarn add axios in your app terminal to get access to the API queries. Import axios and use it in a .get function.

It would be best to create another state function that will regulate the rates object in your endpoints data containing the credentials of all the latest currencies in the world.

After that, store the state of rates in a response function inside the get function. Lastly, call the ratesobject keys in theCurrencyInput` JSX element.

import { useState, useEffect } from "react";
import axios from "axios";

function App() {
const [rates, setRates] = useState([]);

useEffect(() => {
    axios.get('http://data.fixer.io/api/latest?access_key=106ab470d06b4c14d00c10f864ef62b6')
      .then(response => {
        setRates(response.data.rates);
      })
  }, []);

  return (
<div>
  <CurrencyInput 
  currencies={Object.keys(rates)} 
  />

  <CurrencyInput 
  currencies={Object.keys(rates)} 
  />
</div>
  );
}

The following functionality we will implement is the ability of the input values to update following the set currency automatically. So, head back to your CurrentInput.js and create an onChange function in the input and select tags.

These two will control the value input by the user and the difference in the currency set by the user.

You will also create two functions, onAmountChanged and onCurrencyChanged, that will carry out these tasks and pass them in your app as propTypes. For example, here is the code below:

import React from 'react'
import propTypes from "prop-types"
const CurrencyInput = (props) => {
    return (
    <input type="text" value={props.amount} onChange={event => props.onAmountChange(event.target.value)}  />
            <select value={props.currency} onChange ={event => props.onCurrencyChange(event.target.value)}>
                {props.currencies.map((currency => (
                    <option value={currency}>{currency}</option>
                )))}
                </select>   
        </div>
    )
}

CurrencyInput.propTypes = {
    onAmountChange: propTypes.func,
    onCurrencyChange: propTypes.func
}

The state management functions

The handleAmount1Change function

It would help if you used the rates from fixer.io to re-calculate the values according to the set currency. To do that, create a function in the App.js, call it handleAmount1Change, and pass in amount1 as an argument.

This function will help update the state of the first input element. So, when the values in the first input change, the values in the second input will also change for the currency the user sets.

So, you will setAmount2 to be equal to be amount1 multiplied by the rate of currency2 divided by the rate of currency1.

After that, call onAmountChange in the CurrencyInput component tag and pass in this handleAmount1Change function.

function handleAmount1Change(amount1) {
  setAmount2(format(amount1 * rates[currency2] / rates[currency1]));
  setAmount1(amount1);
}

return (
<div>
<CurrencyInput
        onAmountChange={handleAmount1Change}
        />
</div>
)

The handleCurrency1Change function

Now, create another function called handleCurrency1Change that will handle the state change for the select elements that will handle the change in currencies.

The same code works except that currency1 is passed in the setCurrency1 function this time. Then, call the onCurrencyChange function in the CurrencyInput JSX element and pass in this handleCurrency1Change function.

function handleCurrency1Change(currency1) {
    setAmount2(format(amount1 * rates[currency2] / rates[currency1]));
    setCurrency1(currency1);
  }

  return (
  <div>
  <CurrencyInput
  onCurrencyChange={handleCurrency1Change}
  />
  </div>
  )

The handleAmount2Change function

This function will handle the change in the state of the second input in the app.

Pass in amount2 as an argument. Then, setAmount1 to be equal to amount2 times the rate of currency1 divided by the rate of currency2.

Next, pass in amount2 in the setAmount2 function. After that, call the onAmountChange function in the CurrentInput tag and pass in this handleAmount2Change function.

function handleAmount2Change(amount2) {
   setAmount1(format(amount2 * rates[currency1] / rates[currency2]));
   setAmount2(amount2);
 }

 return (
 <div>
 <CurrencyInput
 onAmountChange={handleAmount2Change}
/>
 </div>
 )

The handleCurrency2Change function

This function will regulate the change in the state of the second select element, which controls whatever currency the user chooses.

Again, the same code as the handleAmount2Change is used here, except that you will call the setCurrency2 and pass in currency2. Now, you can call the onCurrencyChange method in the CurrentInput tag and pass it in handleCurrency2Change.

function handleCurrency2Change(currency2) {
    setAmount1(format(amount2 * rates[currency1] / rates[currency2]));
    setCurrency2(currency2);
  }

  return (
  <div>
  <CurrencyInput
  onCurrencyChange={handleCurrency2Change}
  />
  </div>
  )

The roundUp function

At this point, if you input a value in one currency, the equivalent value in another currency might be a number with many decimals. So, this function will help round up all the input values to a maximum of four decimal places.

function roundUp(number) {
   return number.toFixed(4);
 }

After that, call this roundUp method in the four-state management functions you just created.

One more thing you have to do is set the app’s default state when the user reloads the page. You can do that with another useEffect.

Put a conditional statement inside the useEffect saying “if rates is not empty, then call the handleAmount1Change and set its default state to 1 else, call an init function.”

Here is the code below:

import { useEffect } from "react";
function App() {
useEffect(() => {
    if (!!rates) {
      function init() {
        handleAmount1Change(1);
      }
      init();
    }
  }, [rates]);
}

At this point, here is what the application looks like:

currency-converter

Here is a video of the app in action:

Conclusion

While building the currency converter, we used ReactJS and its hooks to implement its functionalities. We also styled the application with CSS3 and React’s Material UI components. With that, you have a completely functional currency converter. You can get the source code from my Github Repo.


Peer Review Contributions by: Mercy Meave