Handling File Fields using React Hook Form

In this article, we will learn how to handle file uploads using 

 is a great library that provides an easy way to build forms with React. It provides a number of 

 that simplify the process of defining and validating various types of form fields. In the following sections, we will learn how to define a file input, and use it to upload files to 

 to generate a stock React app. We'll call our app 

npx create-react-app react-hook-form-file-input

Once the app is ready, we can navigate into the folder and install 

cd react-hook-form-file-input
yarn add react-hook-form

 file. We can remove all the default markup added by 

 element which contains a file input and a submit button like so:

import React from "react";

function App() {
  return (
    <form>
      <input type="file" name="picture" />
      <button>Submit</button>
    </form>
  );
}

export default App;


 function which, as the name suggests, connects a given element with 

import React from "react";
import { useForm } from "react-hook-form";

function App() {
  const { register } = useForm();

  return (
    <form>
      <input ref={register} type="file" name="picture" />
      <button>Submit</button>
    </form>
  );
}

export default App;


Now that our file input has been registered, we can handle submissions by adding an 

import React from "react";
import { useForm } from "react-hook-form";

function App() {
  const { register, handleSubmit } = useForm();

  const onSubmit = (data) => {
    console.log(data);
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input ref={register} type="file" name="picture" />
      <button>Submit</button>
    </form>
  );
}

export default App;


 is an object whose keys are the names of the fields, and values are the values of the respective fields.

On choosing a file and clicking 'Submit', details about the uploaded file will be logged to the console.

Now that we have learnt how to work with file inputs using 

, let us look at a slightly more advanced use case for uploading files to 

You can find the code for the Firebase file upload example 

git clone https://github.com/satansdeer/firebase-file-upload
yarn

You can set up your Firebase configuration in the 

 files at the root of the project, and log into Firebase using the 

 file contains a file input which uploads a file to Firebase.

import React from 'react';
import './App.css';
import {app} from './base'

function App() {
  const onChange = (e) => {
    const file = e.target.files[0];
    const storageRef = app.storage().ref()
    const fileRef = storageRef.child(file.name)
    fileRef.put(file).then(() => {
      console.log("Uploaded a file")
    })
  }

  return (
    <input type="file" onChange={onChange}/>
  );
}

export default App;


import React from "react";
import "./App.css";
import { app } from "./base";
import { useForm } from "react-hook-form";

function App() {
  const { register, handleSubmit } = useForm();

  const onSubmit = (data) => {
    const file = data.image[0];
    const storageRef = app.storage().ref();
    const fileRef = storageRef.child(file.name);
    fileRef.put(file).then(() => {
      console.log("Uploaded a file");
    });
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input
        ref={register}
        name="image"
        type="file" />
    </form>
  );
}

export default App;


 command and it will look the same as earlier.

Choosing a file and clicking 'Submit' will upload it to Firebase.

We have now learnt how to work with file inputs using 

The code used in this article is available at  

https://github.com/satansdeer/react-hook-form-file-input

https://github.com/satansdeer/firebase-file-upload

<h1 data-node-type="titlePlaceholder" class="titlePlaceholder">Handling File Fields using React Hook Form</h1><div data-node-type="summary" class="summary-block">In this article, we will learn how to handle file uploads using <code>react-hook-form</code>.</div><p><code><a href="https://react-hook-form.com/" rel="noopener noreferrer nofollow">react-hook-form</a></code> is a great library that provides an easy way to build forms with React. It provides a number of <a href="https://reactjs.org/docs/hooks-intro.html" rel="noopener noreferrer nofollow">hooks</a> that simplify the process of defining and validating various types of form fields. In the following sections, we will learn how to define a file input, and use it to upload files to <a href="https://firebase.google.com/" rel="noopener noreferrer nofollow">firebase. </a></p><h3><a name="prerequisites" id="prerequisites">Prerequisites</a></h3><ul><li><p><a href="https://nodejs.org/en/download/" rel="noopener noreferrer nofollow">Node.js</a> and <code><a href="https://yarnpkg.com/" rel="noopener noreferrer nofollow">yarn</a></code>.</p></li><li><p><a href="https://code.visualstudio.com/" rel="noopener noreferrer nofollow">Visual Studio Code</a> (or another code editor of your choice).</p></li><li><p>Fair working knowledge of JavaScript and <a href="https://reactjs.org/" rel="noopener noreferrer nofollow">React</a>.</p></li><li><p>A firebase account to upload files to.</p></li></ul><h2><a name="part-1-simple-file-field" id="part-1-simple-file-field">Part 1: Simple File Field</a></h2><h3><a name="step-1-set-up-react-app-🏗" id="step-1-set-up-react-app-🏗">Step 1: Set up React App 🏗</a></h3><p>We will use <code>create-react-app</code> to generate a stock React app. We'll call our app <code>react-hook-form-file-input</code>.</p><textarea data-iscodemirror="true" data-mode="text/x-sh" data-uniqueid="cm-DlAuH" id="cm-DlAuH">npx create-react-app react-hook-form-file-input</textarea><p>Once the app is ready, we can navigate into the folder and install <code><a href="https://react-hook-form.com/" rel="noopener noreferrer nofollow">react-hook-form</a></code>.</p><textarea data-iscodemirror="true" data-mode="text/x-sh" data-uniqueid="cm-WiE8q" id="cm-WiE8q">cd react-hook-form-file-input
yarn add react-hook-form</textarea><h3><a name="step-2-defining-our-form-📋" id="step-2-defining-our-form-📋">Step 2: Defining our form 📋</a></h3><p>Let us define our form in the <code>app.js</code> file. We can remove all the default markup added by <code>create-react-app</code>, and add a <code>form</code> element which contains a file input and a submit button like so:<br></p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-swSIx" id="cm-swSIx">import React from "react";

function App() {
  return (
    &lt;form&gt;
      &lt;input type="file" name="picture" /&gt;
      &lt;button&gt;Submit&lt;/button&gt;
    &lt;/form&gt;
  );
}

export default App;
</textarea><p></p><h3><a name="step-3-adding-react-hook-form-🪝" id="step-3-adding-react-hook-form-🪝">Step 3: Adding <code>react-hook-form 🪝</code></a></h3><p>We can now connect our <code>form</code> element to <code>react-hook-form</code> using the <code>useForm</code> hook. <code>useForm</code> returns an object containing a <code>register</code> function which, as the name suggests, connects a given element with <code>react-hook-form</code>. </p><p>We need to pass the <code>register</code> function as a <code>ref</code> into each element we want to connect.</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-h37B5" id="cm-h37B5">import React from "react";
import { useForm } from "react-hook-form";

function App() {
  const { register } = useForm();

  return (
    &lt;form&gt;
      &lt;input ref={register} type="file" name="picture" /&gt;
      &lt;button&gt;Submit&lt;/button&gt;
    &lt;/form&gt;
  );
}

export default App;
</textarea><p>Now that our file input has been registered, we can handle submissions by adding an <code>onSubmit</code> handler to the form. The <code>useForm</code> hook also returns a <code>handleSubmit</code> function with which we will wrap our <code>onSubmit</code> handler.</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-tYC4s" id="cm-tYC4s">import React from "react";
import { useForm } from "react-hook-form";

function App() {
  const { register, handleSubmit } = useForm();

  const onSubmit = (data) =&gt; {
    console.log(data);
  };

  return (
    &lt;form onSubmit={handleSubmit(onSubmit)}&gt;
      &lt;input ref={register} type="file" name="picture" /&gt;
      &lt;button&gt;Submit&lt;/button&gt;
    &lt;/form&gt;
  );
}

export default App;
</textarea><p>The <code>data</code> parameter that is passed to <code>onSubmit</code> is an object whose keys are the names of the fields, and values are the values of the respective fields.</p><p>In our case, <code>data</code> will have just one key - <code>picture</code>, whose value will be a <code>FileList</code>.</p><h3><a name="step-4-try-it-out-🚀" id="step-4-try-it-out-🚀">Step 4: Try it out! 🚀</a></h3><p>When we fire up the app using <code>yarn start</code>, we will see this on screen.</p><figure class="photo figure-position-inline"><img src="https://s3.amazonaws.com/assets.fullstack.io/n/20201129200642568_Screenshot%202020-11-29%20at%2020.06.23.png" attachmentid="e057f81b-c576-4cbc-9b82-bf3b308a5b1b" contenteditable="false" data-width="936" data-height="576"><div></div></figure><p>On choosing a file and clicking 'Submit', details about the uploaded file will be logged to the console.</p><figure class="photo figure-position-inline"><img src="https://s3.amazonaws.com/assets.fullstack.io/n/20201129200558182_Screenshot%202020-11-29%20at%2020.05.00.png" attachmentid="b8b55908-0248-4fd0-bade-41a5560b6efa" contenteditable="false" data-width="1226" data-height="530"><div></div></figure><p></p><p>Now that we have learnt how to work with file inputs using <code>react-hook-form</code>, let us look at a slightly more advanced use case for uploading files to <a href="https://firebase.google.com/" rel="noopener noreferrer nofollow">Firebase</a>.</p><h2><a name="part-2-uploading-files-to-firebase" id="part-2-uploading-files-to-firebase">Part 2: Uploading files to Firebase</a></h2><h3><a name="step-1-clone-the-code-👩‍💻" id="step-1-clone-the-code-👩‍💻">Step 1: Clone the code 👩‍💻</a></h3><p>You can find the code for the Firebase file upload example <a href="https://github.com/satansdeer/firebase-file-upload" rel="noopener noreferrer nofollow">here</a>. Clone the repo and run <code>yarn</code> to install the dependencies.</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-0JYtX" id="cm-0JYtX">git clone https://github.com/satansdeer/firebase-file-upload
yarn</textarea><p>You can set up your Firebase configuration in the <code>.firebaserc</code> and <code>firebase.json</code> files at the root of the project, and log into Firebase using the <a href="https://firebase.google.com/docs/cli" rel="noopener noreferrer nofollow">CLI</a>.</p><h3><a name="step-2-add-react-hook-form" id="step-2-add-react-hook-form">Step 2: Add <code>react-hook-form</code></a></h3><p>As we've seen earlier, we can install <code>react-hook-form</code> via <code>yarn</code> using:</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-8uYTa" id="cm-8uYTa">yarn add react-hook-form</textarea><p>The <code>App.js</code> file contains a file input which uploads a file to Firebase.</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-MEl6G" id="cm-MEl6G">import React from 'react';
import './App.css';
import {app} from './base'

function App() {
  const onChange = (e) =&gt; {
    const file = e.target.files[0];
    const storageRef = app.storage().ref()
    const fileRef = storageRef.child(file.name)
    fileRef.put(file).then(() =&gt; {
      console.log("Uploaded a file")
    })
  }

  return (
    &lt;input type="file" onChange={onChange}/&gt;
  );
}

export default App;
</textarea><p>We can now switch it over to use <code>react-hook-form</code> like so:</p><textarea data-iscodemirror="true" data-mode="text/jsx" data-uniqueid="cm-Qc242" id="cm-Qc242">import React from "react";
import "./App.css";
import { app } from "./base";
import { useForm } from "react-hook-form";

function App() {
  const { register, handleSubmit } = useForm();

  const onSubmit = (data) =&gt; {
    const file = data.image[0];
    const storageRef = app.storage().ref();
    const fileRef = storageRef.child(file.name);
    fileRef.put(file).then(() =&gt; {
      console.log("Uploaded a file");
    });
  };

  return (
    &lt;form onSubmit={handleSubmit(onSubmit)}&gt;
      &lt;input
        ref={register}
        name="image"
        type="file" /&gt;
    &lt;/form&gt;
  );
}

export default App;
</textarea><p>We have wrapped the <code>input</code> element with a <code>form</code>, given it a <code>name</code> and registered it with <code>react-hook-form</code>.</p><p>We have also moved all the logic in the <code>onChange</code> event handler into our <code>onSubmit</code> handler which receives the data from <code>react-hook-form</code>.</p><h3><a name="step-3-try-it-out-🚀" id="step-3-try-it-out-🚀">Step 3: Try it out! 🚀</a></h3><p>We can run the app using the <code>yarn start</code> command and it will look the same as earlier.</p><figure class="photo figure-position-null"><img src="https://s3.amazonaws.com/assets.fullstack.io/n/20201129200642568_Screenshot%202020-11-29%20at%2020.06.23.png" attachmentid="e057f81b-c576-4cbc-9b82-bf3b308a5b1b" contenteditable="false" data-width="936" data-height="576"><div></div></figure><p>Choosing a file and clicking 'Submit' will upload it to Firebase.</p><figure class="photo figure-position-inline"><img src="https://s3.amazonaws.com/assets.fullstack.io/n/20201129203443343_Screenshot%202020-11-29%20at%2020.34.06.png" attachmentid="08b2a9c7-a96f-4dc6-9025-0edb0f7455d6" contenteditable="false" data-width="1654" data-height="1110"><div></div></figure><p></p><p>We have now learnt how to work with file inputs using <code>react-hook-form</code>. ✅</p><p>The code used in this article is available at  <a href="https://github.com/satansdeer/react-hook-form-file-input" rel="noopener noreferrer nofollow">https://github.com/satansdeer/react-hook-form-file-input</a> and <a href="https://github.com/satansdeer/firebase-file-upload" rel="noopener noreferrer nofollow">https://github.com/satansdeer/firebase-file-upload</a>.</p>

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Maksim Ivanov

In this article, we will learn how to handle file uploads using react-hook-form.

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