The idea behind creating a quick response (QR) code generator is to translate data from images to text. A QR code is simply the representation of image data as text, and it has a lot of useful applications from restaurant menus and concert tickets, to online calendar invites, payments, and the list goes on. In this tutorial, you will learn how to create a QR code using the JavaScript library, React. The benefit of using React is that it makes building frontend applications a breeze as it provides developers ways to reuse components. To follow through this tutorial, the following will be covered: Prerequisites Getting started Creating a QR code generator Styling the QR code app Downloading the generated QR code Conclusion Resources Demo Prerequisites To complete this tutorial, you need the following: Basic understanding of React.js installed on your local machine Node >= 14.0.0 and npm >= 5.6 Getting Started Before writing a line of code, open your terminal and run the following command: npx create-react-app qrcode-generator The command above scaffolds the files and installs a few packages needed to create the React app. Next, navigate to the project directory and run the development server which is accessible on using the command below to preview the app in the browser: http://localhost:3000 npm start cd qrcode-generator Finally, let’s install the dependency library required for creating the QR code generator. Run the command: npm install qrcode.react : A React component to generate QR codes for rendering to the DOM. qrcode.react Creating a QR Code Generator Great work so far! The creation of the QR code generator will begin with creating the files and components that will contain the structure of the QR code. Inside the src directory, create a folder called components and a file named QrCode.js in the folder. Copy and paste the following code: e.preventDefault(); }; setUrl(e.target.value);
  }; ); );
}; // src/components/QrCode.js import { useState } from "react" ; import { QRCodeCanvas } from "qrcode.react" ; const QrCode = () => { const [url, setUrl] = useState( "" ); const downloadQRCode = ( e ) => { setUrl( "" ); const qrCodeEncoder = ( e ) => { const qrcode = ( < QRCodeCanvas id = "qrCode" value = {url} size = {300} bgColor = { "# 00ff00 "} level = { " H "} /> return ( < div className = "qrcode__container" > < div > {qrcode} </ div > < div className = "input__group" > < form onSubmit = {downloadQRCode} > < label > Enter URL </ label > < input type = "text" value = {url} onChange = {qrCodeEncoder} placeholder = "https://hackernoon.com" /> < button type = "submit" disabled = {!url} > Download QR code </ button > </ form > </ div > </ div > export default QrCode; The code snippets above do the following: Import is used to declare the initial state of the variable, url which is set to an empty string, and the function, used to update the state useState setState setUrl The library, , is used to render the generated QR code qrcode.react Next, the use of the function attached to the method of the element as this is triggered by the submit event downloadQRCode onSubmit <form> On the element, the event handler with the function takes in the users’ input, gets its value and changes the QR code with each new input typed <input> onChange ‘qrCodeEncoder’ A variable is created.  It takes in the component and passes some available prompts that customize and make the QR code visible on the browser. Check out the documentation to learn more about the in the component qrcode QRCodeCanvas use of props Finally, the element is disabled until the user input receives data <button> Styling the QR Code App In the folder, create the stylesheet, responsible for the visual appeal of the app src styles.css Copy and paste the following code: *,
*:before,
*:after { } } } } } } } } } } } } } }
} /* src/styles.css */ margin: 0 ; padding : 0 ; box-sizing : border-box; :root { -- font - color : 230 35% 7% ; body { color : hsl ( var (--font-color)); img { max-width : 100% ; display : block; .section { padding : 2em 0 ; display : flex; min-height : 100vh ; align-items : center; .container { margin -inline: auto; max-width : 75rem ; width : 85% ; .input__group { display : flex; margin-top : 2em ; input { width : 100% ; padding : 1em 0.75em ; border : 1px solid #444343 ; border-radius : 3px ; margin-bottom : 2em ; margin-top : 0.75em ; button { border : unset; background : hsl ( 231 , 77% , 90% ); padding : 1em 0.75em ; color : hsl ( var (--font-color)); cursor : pointer; text-transform : uppercase; font-weight : bold; @media screen and ( min-width : 768px ) { .section { padding : 0 ; input { margin : 0 ; .qrcode__container { display : flex; align-items : center; .input__group { margin-left : 3em ; input { margin-bottom : 2em ; margin-top : 0.75em ; font-size : 1rem ; Next, import the QrCode.js file and stylesheet in the entry point of the app, App.js: );
} // src/App.js import QrCode from "./components/QrCode" ; import "./styles.css" ; export default function App ( ) { return ( < div className = "section container" > < QrCode /> </ div > With the steps complete, the app should look like this: Downloading the Generated QR Code The option for users to download the generated QR code (created using a ) makes it useful in a wide variety of use cases. From printing the code to embedding it on a website, the use cases are unlimited. QR Code generator Back in the file, let’s update the codebase to use to access the document object model (DOM) nodes. components/QrCode.js refs ... ); );
}; // src/components/QrCode.js import { useState, useRef } from "react" ; // other import const QrCode = () => { const [url, setUrl] = useState( "" ); const qrRef = useRef(); // include this: call the useRef function const qrcode = ( < QRCodeCanvas id = "qrCode" value = {url} size = {300} bgColor = { "# 00ff00 "} level = { " H "} /> return ( < div className = "qrcode__container" > < div ref = {qrRef} > {qrcode} </ div > {/* include this */} {/* form input container */} </ div > export default QrCode; Now, let’s update the function in the file to be able to click the download QR code button and save the canvas as an image file. downloadQRCode QrCode.js e.preventDefault(); anchor.href = image; anchor.click(); };
  ... );
}; // src/components/QrCode.js // imports const QrCode = () => { // state // useRef const downloadQRCode = ( e ) => { let canvas = qrRef.current.querySelector( "canvas" ); let image = canvas.toDataURL( "image/png" ); let anchor = document .createElement( "a" ); anchor.download = `qr-code.png` ; document .body.appendChild(anchor); document .body.removeChild(anchor); setUrl( "" ); return ( < div className = "qrcode__container" > < div ref = {qrRef} > {qrcode} </ div > {/* form input container */} </ div > export default QrCode; In the function, the following takes place: downloadQRCode It references the current value of the ref object with the .current property to know when the node changes The component produces the canvas element in the DOM which gives you the ability to create content dynamically qrcode.react The canvas is appended to the method with the specified type parameter set to the file formate, toDataURL image/png Next, the anchor, element is created and the is set to the image that downloads the QR code when the button is clicked <a> href The anchor element is appended to the document body and once the QR code is downloaded, it is removed Finally, the state url is updated with the variable which clears the input for the generated QR code as the form is submitted setUrl The complete code for the component QrCode.js: e.preventDefault(); anchor.href = image; anchor.click(); }; setUrl(e.target.value);
  }; ); );
}; import { useState, useRef } from "react" ; import { QRCodeCanvas } from "qrcode.react" ; const QrCode = () => { const [url, setUrl] = useState( "" ); const qrRef = useRef(); const downloadQRCode = ( e ) => { let canvas = qrRef.current.querySelector( "canvas" ); let image = canvas.toDataURL( "image/png" ); let anchor = document .createElement( "a" ); anchor.download = `qr-code.png` ; document .body.appendChild(anchor); document .body.removeChild(anchor); setUrl( "" ); const qrCodeEncoder = ( e ) => { const qrcode = ( < QRCodeCanvas id = "qrCode" value = {url} size = {300} bgColor = { "# 00ff00 "} level = { " H "} /> return ( < div className = "qrcode__container" > < div ref = {qrRef} > {qrcode} </ div > < div className = "input__group" > < form onSubmit = {downloadQRCode} > < label > Enter URL </ label > < input type = "text" value = {url} onChange = {qrCodeEncoder} placeholder = "https://hackernoon.com" /> < button type = "submit" disabled = {!url} > Download QR code </ button > </ form > </ div > </ div > export default QrCode; The final result of the app should look like this: Conclusion This tutorial described the process of creating a QR code generator and how it can be downloaded for later use. Resources QR Code The anchor element All about QR code

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