Dynamic web worker

webworker.js

function createWorker(fn) {
  // Create a Blob object that contains the code for the worker
  // create wrapper function that calls the function passed to createWorker
  // and then posts the result back to the main thread

  const fnStr = fn.toString()

  // wrap the function in a function that calls the function and posts the result
  const wrapper = `async function(evt) {
    const fn = ${fnStr}
    try {
      const result = await fn(...evt.data)
      postMessage(result)
    } catch (e) {
      postMessage(e)
    }
  }`

  var blob = new Blob(['self.onmessage = ', wrapper], {
    type: 'text/javascript',
  })

  // Create an object URL for the blob
  var url = window.URL.createObjectURL(blob)

  // Create a new Worker using the object URL
  var worker = new Worker(url)

  // Return an async function that can be used to run the worker's function and receive the result
  return async function (...args) {
    // Send a message to the worker with the arguments for the function
    worker.postMessage(JSON.parse(JSON.stringify(args)))

    // Wait for the response from the worker
    return new Promise((resolve, reject) => {
      worker.addEventListener('message', event => {
        // Resolve the promise with the result from the worker
        resolve(event.data)
      })
    })
  }
}

const getTodo = createWorker(async id => {
    return fetch('https://jsonplaceholder.typicode.com/todos/' + id).then(response => response.json())
      .then(json => console.log(json))
 })
 
const result = await getTodo(2)
console.log('todo:', result)