Upload a File from React to a Flask API

flask_backend.py

# the flask post request receiver
from io import BytesIO
from flask import jsonify, request

@app.route('/url_route', methods=['POST'])
def upload_file():
    """Handles the upload of a file."""
    d = {}
    try:
        file = request.files['file_from_react']
        filename = file.filename
        print(f"Uploading file {filename}")
        file_bytes = file.read()
        file_content = BytesIO(file_bytes).readlines()
        print(file_content)
        d['status'] = 1

    except Exception as e:
        print(f"Couldn't upload file {e}")
        d['status'] = 0

    return jsonify(d)

react_frontend.js

// the react post request sender
uploadFile = async (e) => {
  const file = e.target.files[0];
  if (file != null) {
    const data = new FormData();
    data.append('file_from_react', file);

    let response = await fetch('/url_route',
      {
        method: 'post',
        body: data,
      }
    );
    let res = await response.json();
    if (res.status !== 1){
      alert('Error uploading file');
    }
  }
};
  
// the react form
<form>
  <input
    type="file"
    onChange={this.uploadFile}>
  </input>
</form>