javascript - react js handling file upload

Question

I'm new to react js. I want to upload image asynchronously with react js Suppose I have this code

var FormBox = React.createClass({
  getInitialState: function () {
    return {
      photo: []
    }
  },
  pressButton: function () {
    var data = new FormData();
    data.append("photo", this.state.photo);
    // is this the correct way to get file data?
  },
  getPhoto: function (e) {
    this.setState({
      photo: e.target.files[0]
    })
  },
  render: function () {
    return (
      <form action='.' enctype="multipart/form-data">
        <input type='file'  onChange={this.getPhoto}/>
        <button onClick={this.pressButton}> Get it </button>
      </form>
    )
  }
})

ReactDOM.render(<FormBox />, document.getElementById('root'))

Any answer will be appreciated!

Answer 1

You can make use of FileReader

var FormBox = React.createClass({
          getInitialState: function () {
            return {
              file: '',
              imagePreviewUrl: ''
            }
          },
          pressButton: function () {
            e.preventDefault();
          // TODO: do something with -> this.state.file
          console.log('handle uploading-', this.state.file);
          },
          getPhoto: function (e) {
            e.preventDefault();

            let reader = new FileReader();
            let file = e.target.files[0];

            reader.onloadend = () => {
              this.setState({
                file: file,
                imagePreviewUrl: reader.result
              });
            }

            reader.readAsDataURL(file);
            
          },
          render: function () {
            let {imagePreviewUrl} = this.state;
            let imagePreview = null;
            if (imagePreviewUrl) {
              imagePreview = (<img src={imagePreviewUrl} />);
            } else {
              imagePreview = (<div className="previewText">Please select an Image for Preview</div>);
            }
            return (
              <div>
              <form action='.' enctype="multipart/form-data">
                <input type='file'  onChange={this.getPhoto}/>
                <button onClick={this.pressButton}> Get it </button>
              </form>
              <div className="imgPreview">
                {imagePreview}
              </div>
              </div>
            )
          }
        })
        
        ReactDOM.render(<FormBox />, document.getElementById('root'))

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react-dom.min.js"></script>
<div id="root"></div>