How you upload files in React is similar to how you upload files in plain HTML and JavaScript.  

We use the `<input type="file">` HTML element and handle upload events in React components.

# Example

Here is an example of uploading and displaying an image file.  
We make a `FileUpload` component and store the file object in its state. Using `event.target`, we get the uploaded image file, update the component state, and finally display the image and its details.  

Similarly, you can also upload and handle any file by slightly tweaking the code below.

import React from "react";
require("./style.css");

import ReactDOM from "react-dom";
import App from "./app.js";

ReactDOM.render(
  <App />,
  document.getElementById("root")
);


import React from "react";

/**
 * Component to handle file upload. Works for image
 * uploads, but can be edited to work for any file.
 */
function FileUpload() {
  // State to store uploaded file
  const [file, setFile] = React.useState("");

  // Handles file upload event and updates state
  function handleUpload(event) {
    setFile(event.target.files[0]);

    // Add code here to upload file to server
    // ...
  }

  return (
    <div id="upload-box">
      <input type="file" onChange={handleUpload} />
      <p>Filename: {file.name}</p>
      <p>File type: {file.type}</p>
      <p>File size: {file.size} bytes</p>
      {file && <ImageThumb image={file} />}
    </div>
  );
}

/**
 * Component to display thumbnail of image.
 */
const ImageThumb = ({ image }) => {
  return <img src={URL.createObjectURL(image)} alt={image.name} />;
};


export default function App() {
  return <FileUpload />;
}


img {
  height: 100px;
  width: 100px;
}


import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


React

Dart

GoJS React

Typescript React

Vue.js

File upload in React

Use `<input type="file">` for file uploads in React, handling events to update state and display files.