Native / pure / no-npm file upload REST API

native-node-file-upload.js

/**
 * This is native /pure /no-npm node.js file uploader.
 *
 * CLIENT FUNCTION: export function uploadFile(file) {
 * fetch("http://localhost:8080/sys/upload", {
 * method: 'POST',
 * headers: { "Content-Type": "multipart/form-data;"},
 * body: file }).then(response => response.json()
 * ).then(
 * success => console.log(success)
 * ).catch(
 * error => console.log(error)
 * );
 * }
 *
 */

const http = require('http');
const url = require('url');
const fs = require('fs');

const route = {};
// handler for /hello endpoint
route.hello = function(data, callback) {
  callback(200, {res: 'Hello World'});
};
// handler for admin/env endpoint
route.env = function(data, callback) {
  callback(200, (function() {
    if (process.env.PROD !== undefined) {
      return {res: 'PROD'};
    } else if (process.env.DEV !== undefined) {
      return {res: 'DEV'};
    } else {
      return {res: 'LOCALHOST'};
    }
  })());
};
// handler for sys/upload endpoint
route.upload = function(data, callback) {
  console.log('Upload started');

  saveFile(data).then(
    (result) => {
      callback(200, {res: 'File successfully uploaded: ' + result});
      console.log('Upload finished');
    },
    (error) => {
      callback(500, {res: 'File was not uploaded: ' + error});
      console.log('Upload failed');
    },
  );
};
// default handler
route.notFound = function(data, callback) {
  callback(404);
};
// path router
const router = function(path) {
  switch (path) {
    case 'hello':
      return route.hello;
    case 'sys/env':
      return route.env;
    case 'sys/upload':
      return route.upload;
    default:
      return route.notFound;
  }
};

// hardcoded multipart parser roughly based on https://www.w3.org/Protocols/rfc1341/7_2_Multipart.html
function multipartParser(body) {
  body = body.split('\r\n');
  const jsonBody = {};
  for (let i = 0; i < body.length; i++) {
    const arrayPart = body[i];
    if (arrayPart.includes('name=')) {
      const fieldName = arrayPart.substring(
        arrayPart.indexOf('name=') + 6, arrayPart.lastIndexOf('"'));
      jsonBody[fieldName] = body[i + 2];
    }
  }
  return {body, jsonBody};
}

function saveFile(data) {
  const saveName = data.body.originalFileName;
  const base64Data = data.body.file.replace(/^data:[a-z]*\/[a-z]*;base64/, '');

  return new Promise(function(resolve, reject) {
    fs.writeFile(`./uploaded_base64Data_${saveName}`, base64Data, 'base64',
      function(err) {
        if (err) reject(err);
        else resolve(data);
      }
    );
  });
}

const server = http.createServer(function(req, res) {
  // enable cors
  res.setHeader('Access-Control-Allow-Origin', 'http://localhost:3000');
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE, HEAD');
  res.setHeader('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  res.setHeader('Access-Control-Allow-Credentials', 'true');
  // parse the requested url
  const requestUrl = url.parse(req.url, true);
  console.log('requestUrl: ' + requestUrl);
  // parse the trimmed path which we will use in the router
  const routePath = requestUrl.pathname.replace(/^\/+|\/+$/g, '');
  console.log('routePath: ' + routePath);
  let body = [];
  // push the chunked data into the body array
  req.on('data', function(chunk) { // https://developer.mozilla.org/en-US/docs/Web/API/Streams_API https://nodejs.org/api/stream.html
    body.push(chunk);
  });

  // handle the data coming from request
  req.on('end', function() {
    const routeHandler = router(routePath);
    body = Buffer.concat(body).toString();
    const __ret = multipartParser(body);
    const jsonBody = __ret.jsonBody;
    const data = {
      'routePath': routePath,
      'query': requestUrl.query,
      'method': req.method,
      'headers': req.headers,
      'body': jsonBody,
    };

    routeHandler(data, function(statusCode, payload) {
      statusCode = typeof (statusCode) === 'number' ? statusCode : 200;
      payload = typeof (payload) === 'object' ? payload : {};

      res.writeHead(statusCode);
      res.end(payload.res);

      console.log('Response: ', statusCode, payload.res);
    });
  });
});

server.listen(8080, function() {
  console.log('Server started on port 8080!');
});