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

  • By
    How to Create a RetroPie on Raspberry Pi – Graphical Guide

    Today we get to play amazing games on our super powered game consoles, PCs, VR headsets, and even mobile devices.  While I enjoy playing new games these days, I do long for the retro gaming systems I had when I was a kid: the original Nintendo...

  • By
    An Interview with Eric Meyer

    Your early CSS books were instrumental in pushing my love for front end technologies. What was it about CSS that you fell in love with and drove you to write about it? At first blush, it was the simplicity of it as compared to the table-and-spacer...

Incredible Demos

  • By
    Instagram For MooTools

    If you're still rocking an iPhone and fancy taking a photo every now and then, you'd be crazy not to be using an app called Instagram.  With Instagram you take the photos just as you would with your native iPhone camera app, but Instagram...

  • By
    MooTools dwCheckboxes Plugin

    Update / Fix: The checkboxes will no longer toggle when the "mouseup" event doesn't occur on a checkbox. Every morning I wake up to a bunch of emails in my Gmail inbox that I delete without reading. I end up clicking so many damn checkboxes...

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!