how to upload a file in javascript reactj
How to commencement upload file with React and Nodejs
In this tutorial, we become through building a full-stack file upload solution with express and React.js
we gonna create a basic form for handle file upload with React and server-side with Nodejs this tutorial is so simple you can follow forth with 5 minutes information technology should be done if you lot recollect TLDR; just check finish code hither and live demo will host on Codesandbox
Setting upwards the Node server
If you're post-obit for the full tutorial, the complete server code is available. Go to server directory, open concluding and execute npm install and node alphabetize , this will run the server. So keep from the React section.
- Create a directory upload-server, open concluding in this directory and run
npm init. Have all defaults. - In the aforementioned final, install upload and cors packet volition control
npm express express-fileupload cors
start on index.js is the entry file.
Hither's the Initial code for the server.
const PORT = 5000;
const limited = require('limited');
const cors = require('cors'); const app = express();
app.use(cors());
app.get('/', (req, res) => {
return res.condition(200).send("It'south working");
}); app.listen(PORT, () => {
console.log('Server Running sucessfully.');
});
Now, become to your browser at localhost:5000 and you should run across It's working.
Upload Endpoint
Let'south define /upload at the upload endpoint. It needs the middleware fileUpload, ready this affair first.
app.utilise(
fileUpload({
useTempFiles: true,
safeFileNames: true,
preserveExtension: true,
tempFileDir: `${__dirname}/public/files/temp`
})
); It accepts many options, which you lot can find here.
The temporary directory is used to store files temporarily instead of using computer retentivity(RAM). This is very useful in uploading big files.
Safe File removes non-alphanumeric characters from except dash and underscores from the filename. You can also define regex instead of true for custom names.
preserveExtension preserves the extension of the file proper noun, this is faux past default. It besides supports customizations, refer to the documentation for options.
app.post('/upload', (req, res, next) => {
let uploadFile = req.files.file;
const name = uploadFile.proper name;
const md5 = uploadFile.md5();
const saveAs = `${md5}_${name}`;
uploadFile.mv(`${__dirname}/public/files/${saveAs}`, function(err) {
if (err) {
render res.status(500).send(err);
}
return res.status(200).json({ status: 'uploaded', name, saveAs });
});
}); The file in req.files.file refers to file as a name in the input field. That is Name in both <input proper name="Name" type="file" /> and req.file.NAME should be the same.
To prevent overwriting the files, I used an md5 function from the uploadFile package and saved the file as md5_filename.ext .
You can exam the API using Postman as well.
Ship a post request to /upload with a file. It should successfully go through.
React Front End
A server is waiting for files, you need an interface to let users to input the files. Allow'due south create an interface using React.
Prepare up the react application with create-react-app.
npx create-react-app upload-front
Put a class with input type file in App.js. It should await like the post-obit:
import React, { Component } from 'react'; grade App extends Component {
render() {
return (
<class className="App">
<input type="file" proper name="file" />
<push button>Upload</push button>
</class>
);
}
} export default App;
The button won't upload past itself. Define a few methods and states to attain functionality.
State: selectedFile
Methods: handleFileChange, and handleUpload
Add on change listener as handleFileChange on input. You tin adhere handleFileUpload equally a form submit an action or as click listener on a push. Nosotros'll apply the state to hold file and so it doesn't matter.
Hither's how it looks.
import React, { Component } from 'react'; class App extends Component {
handleFileChange = () => {
// define file change
};
handleUpload = () => {
// define upload
};
return() {
return (
<grade className="App" onSubmit={handleUpload}>
<input type="file" name="file" onChange={handleFileChange} />
<button onClick={handleUpload}>Upload</push>
</form>
);
}
} consign default App;
Do not go on handleUpload on both onClick and onSubmit. 1 is enough.
Handling the file change, nosotros keep track of file and an upload button click.
Treatment file change
handleFileChange = (event) => {
this.setState({
selectedFile: event.target.files[0]
});
}; The file input is an result for the click and files are stored in an array (even in single file upload).
Handling the Upload
To handle the uploading, we'll apply Axios to send ajax asking. Install and import Axios.
npm i axios
import axios from 'axios
handleUpload = (effect) => {
consequence.preventDefault();
const data = new FormData();
data.append('file', this.state.selectedFile, this.state.selectedFile.name);
axios.post(endpoint, data).then((res) => {
console.log(res.statusText);
});
}; A file is sent every bit FormData. It just logs the response text after completing the AJAX request.
While it looks too ugly, uploading should commencement working now.
Loading State
While the file is uploaded successfully, the user doesn't run across the response. Showing the response after the completion is quite simple. Allow's show the progress instead.
axios can take some parameters with the post method. 1 of them is ProgressEvent.
{
onUploadProgress: ProgressEvent => {
this.setState({
loaded: (ProgressEvent.loaded / ProgressEvent.total*100),
} This sets a loaded state to any percentage is completed.
Nosotros also demand to display it, and so wrap information technology in a paragraph outside the form. This volition crash the application as JSX can't return multiple parts. Wrap the render in React Fragment.
Here's the code:
return (
<React.Fragment>
<class className="App" onSubmit={this.handleUpload}>
<input
className="inputfile"
id="file"
type="file"
name="file"
onChange={this.handleFileChange}
/>
<label htmlFor="file">Choose a file</label>
<button onClick={this.handleUpload}>Upload</push button>
</course>
<p>{Math.round(this.state.loaded)}%</p>
</React.Fragment>
); I've given it a label, that nosotros'll play with presently. Math.round is to avoid decimal values.
Only this will throw error initially as the state loaded doesn't even exist.
Initialize the state on a component mount with:
land = { selectedFile: null, loaded: null }; In that location'southward no demand of defining a constructor for a state, if you've been doing that fashion.
Here'south how handleUpload is at present…
handleUpload = (issue) => {
// ascertain upload
event.preventDefault();
const information = new FormData();
data.append('file', this.state.selectedFile, this.state.selectedFile.name);
axios
.post(endpoint, data, {
onUploadProgress: (ProgressEvent) => {
this.setState({
loaded: (ProgressEvent.loaded / ProgressEvent.total) * 100
});
}
})
.then((res) => {
console.log(res.statusText);
});
}; Unuglifying things…
This is how ugly information technology is right at present…
I grabbed CSS from here and moved to index.css.
I also added states uploading, message, and defaultMessage. If it is currently uploading, the loaded state volition show the % completed. Otherwise, the message will exist shown.
The JSX returned has also changed slightly, the react part and methods remain the aforementioned. This comes from that same HTML file.
return (
<grade className="box" onSubmit={this.handleUpload}>
<input
type="file"
name="file-5[]"
id="file-five"
className="inputfile inputfile-iv"
onChange={this.handleFileChange}
/>
<label htmlFor="file-5">
<effigy>
<svg
xmlns="http://www.w3.org/2000/svg"
width="20"
elevation="17"
viewBox="0 0 20 17"
>
<path d="M10 0l-5.2 iv.9h3.3v5.1h3.8v-5.1h3.3l-5.2-4.9zm9.3 11.5l-three.ii-2.1h-2l3.four 2.6h-3.5c-.ane 0-.2.one-.2.1l-.viii 2.3h-6l-.viii-2.2c-.one-.1-.1-.ii-.2-.2h-3.6l3.4-2.6h-2l-3.two 2.1c-.4.3-.7 i-.6 1.5l.half-dozen 3.1c.1.five.7.9 one.2.9h16.3c.6 0 i.1-.4 1.3-.9l.6-three.1c.1-.v-.2-1.ii-.7-1.5z" />
</svg>
</figure>
<span>
{this.land.uploading
? this.country.loaded + '%'
: this.country.message}
</span>
</label>
<button className="submit" onClick={this.handleUpload}>
Upload
</button>
</grade>
); 
After adding some CSS for the push likewise, it looks like:
If you click on the upload button without choosing a file, it'll crash.
This is because the selected file is null, and cypher doesn't have the property of proper name.
To set this, return from the handleUpload method if the selectedFile is null. Also, fix the message to upload get-go then the user gets some feedback on what to do.
handleUpload = (outcome) => {
event.preventDefault();
if (this.state.uploading) return;
if (!this.state.selectedFile) {
this.setState({ message: 'Select a file first' });
return;
}
this.setState({ uploading: truthful });
const data = new FormData();
data.append('file', this.land.selectedFile, this.state.selectedFile.name);
axios
.post(endpoint, information, {
onUploadProgress: (ProgressEvent) => {
this.setState({
loaded: Math.circular(
(ProgressEvent.loaded / ProgressEvent.total) * 100
)
});
}
})
.then((res) => {
this.setState({
selectedFile: nothing,
message: 'Uploaded successfully',
uploading: false
});
console.log(res.statusText);
});
}; Likewise, I've rounded the loaded country itself instead of rounding in the output. If you click upload without selecting the file, the message will change to select a file start.
You tin upload another file before the previous one has finished. We can deal with this by using the unloading state. Just return from the handle upload without uploading if the uploading is true.
if (this.state.uploading) return;
if (!this.land.selectedFile) {
this.setState({ message: 'Select a file start' });
render;
}
this.setState({ uploading: true }); After successfully uploading, it changes the bulletin to Uploaded Successfully while uploading state changes to fake.
handleFileChange is modified to show the file name that's going to upload.
handleFileChange = (event) => {
this.setState({
selectedFile: outcome.target.files[0],
loaded: 0,
bulletin: issue.target.files[0]
? event.target.files[0].proper name
: this.state.defaultmessage
});
}; Fault Handling
If you shut downwardly the server, this application volition all the same endeavour to upload the file and loaded will change to NaN (Not a Number). Since uploading was set truthful, you can't upload even the server comes back as handleUpload is blocked by this.
Add a catch to the postal service asking..
.take hold of((err) => {
this.setState({
uploading: false,
message: 'Failed to upload'
});
}); Crawly, information technology uploads a file while displaying the message on fault and success.
Conclusion
your learn how to basic upload with Reactjs and Nodejs in an piece of cake fashion to continue next step yous can implement validation on client and server or show preview before upload
Source: https://kris101.medium.com/react-file-upload-the-easy-way-with-nodejs-e94c5e81fb8
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