React.js, how to send a multipart/form-data to server

The file is also available in the event:

e.target.files[0]

(eliminates the need for document.querySelector('input[type="file"]').files[0];)

uploadAction(e) {
  const data = new FormData();
  const imagedata = e.target.files[0];
  data.append('inputname', imagedata);
  ...

Note: Use console.log(data.get('inputname')) for debugging, console.log(data) will not display the appended data.

Here is my solution for image upload with preview through axios.

import React, { Component } from 'react';
import axios from "axios";

React Component Class:

class FileUpload extends Component {

    // API Endpoints
    custom_file_upload_url = `YOUR_API_ENDPOINT_SHOULD_GOES_HERE`;


    constructor(props) {
        super(props);
        this.state = {
            image_file: null,
            image_preview: '',
        }
    }

    // Image Preview Handler
    handleImagePreview = (e) => {
        let image_as_base64 = URL.createObjectURL(e.target.files[0])
        let image_as_files = e.target.files[0];

        this.setState({
            image_preview: image_as_base64,
            image_file: image_as_files,
        })
    }

    // Image/File Submit Handler
    handleSubmitFile = () => {

        if (this.state.image_file !== null){

            let formData = new FormData();
            formData.append('customFile', this.state.image_file);
            // the image field name should be similar to your api endpoint field name
            // in my case here the field name is customFile

            axios.post(
                this.custom_file_upload_url,
                formData,
                {
                    headers: {
                        "Authorization": "YOUR_API_AUTHORIZATION_KEY_SHOULD_GOES_HERE_IF_HAVE",
                        "Content-type": "multipart/form-data",
                    },                    
                }
            )
            .then(res => {
                console.log(`Success` + res.data);
            })
            .catch(err => {
                console.log(err);
            })
        }
    }


    // render from here
    render() { 
        return (
            <div>
                {/* image preview */}
                <img src={this.state.image_preview} alt="image preview"/>

                {/* image input field */}
                <input
                    type="file"
                    onChange={this.handleImagePreview}
                />
                <label>Upload file</label>
                <input type="submit" onClick={this.handleSubmitFile} value="Submit"/>
            </div>
        );
    }
}

export default FileUpload;

We just try to remove our headers and it works!

fetch("http://localhost:8910/taskCreationController/createStoryTask", {
      mode: 'no-cors',
      method: "POST",
      body: data
    }).then(function (res) {
      if (res.ok) {
        alert("Perfect! ");
      } else if (res.status == 401) {
        alert("Oops! ");
      }
    }, function (e) {
      alert("Error submitting form!");
    });