How to Create an Async Function via “new Function”

By  on  

One thing I love about JavaScript is that there are many ways to accomplish the same task, one such example being creating functions. There are several patterns for functions; one of the last you see used is the new Function method:

/* new Function(arg1, arg2 (...), body) */
const myFunction = new Function('users', 'salary', 'return users * salary');

What if you want to use this new Function method to create an async function? You need to be a bit clever, and thanks to MDN, we have an answer:

// Shim for allowing async function creation via new Function
const AsyncFunction = Object.getPrototypeOf(async function(){}).constructor;

// Usage
const fetchPage = new AsyncFunction("url", "return await fetch(url);");
fetchPage("/").then(response => { ... });

The usage of Object.getPrototypeOf(async function(){}).constructor is super clever, as a native AsyncFunction doesn't exist. I don't believe that I've ever used the new Function pattern but that doesn't mean you don't! And now you can make them asynchronous!

Recent Features

Incredible Demos

  • By
    Comment Preview Using MooTools

    Comment previewing is an awesome addition to any blog. I've seen really simple comment previewing and some really complex comment previewing. The following is a tutorial on creating very basic comment previewing using MooTools. The XHTML You can set up your XHTML any way you'd like.

  • By
    MooTools TextOverlap Plugin

    Developers everywhere seem to be looking for different ways to make use of JavaScript libraries. Some creations are extremely practical, others aren't. This one may be more on the "aren't" side but used correctly, my TextOverlap plugin could add another interesting design element...

Discussion

  1. Gustavo

    fetch() is already an async function, can you change your example?

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!