Performing File Uploads to REST APIs with multipart/form-data in Node.js

const fs = require('fs');
const FormData = require('form-data');
const axios = require('axios'); // Or use Node's built-in http/https or fetch with a polyfill

// --- Configuration ---
const API_UPLOAD_URL = 'http://localhost:3000/upload'; // Replace with your API endpoint
const FILE_PATH_TO_UPLOAD = './example.txt'; // Path to the file you want to upload
const FIELD_NAME_FOR_FILE = 'document'; // The name of the form field the API expects for the file
const CUSTOM_TEXT_FIELD = 'description'; // An optional additional text field
const CUSTOM_TEXT_VALUE = 'This is a test document upload.';

// --- Create a dummy file for demonstration ---
function createDummyFile(path) {
  if (!fs.existsSync(path)) {
    fs.writeFileSync(path, 'This is the content of the example file.');
    console.log(`Created dummy file: ${path}`);
  }
}
createDummyFile(FILE_PATH_TO_UPLOAD);

async function uploadFileToApi() {
  if (!fs.existsSync(FILE_PATH_TO_UPLOAD)) {
    console.error(`Error: File not found at ${FILE_PATH_TO_UPLOAD}`);
    return;
  }

  const form = new FormData();

  // Append the file
  form.append(FIELD_NAME_FOR_FILE, fs.createReadStream(FILE_PATH_TO_UPLOAD));

  // Append other text fields if needed
  form.append(CUSTOM_TEXT_FIELD, CUSTOM_TEXT_VALUE);
  form.append('userId', '123');

  try {
    console.log('Attempting to upload file...');
    const response = await axios.post(API_UPLOAD_URL, form, {
      headers: {
        ...form.getHeaders(), // Important: getHeaders sets the Content-Type with boundary
        'Authorization': 'Bearer YOUR_API_TOKEN' // If your API requires authentication
      },
      maxBodyLength: Infinity, // For potentially large files
      maxContentLength: Infinity // For potentially large files
    });

    console.log('File upload successful!');
    console.log('Status:', response.status);
    console.log('Response data:', response.data);
  } catch (error) {
    if (error.response) {
      console.error('File upload failed with response:', error.response.status, error.response.data);
    } else if (error.request) {
      console.error('File upload failed, no response received:', error.request);
    } else {
      console.error('File upload failed with error:', error.message);
    }
  }
}

uploadFileToApi();