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
    MooTools: Set Style Per Media

    I'd bet one of the most used MooTools methods is the setStyle() method, which allows you to set CSS style declarations for an element. One of the limitations of MooTools' setStyle() method is that it sets the specific style for all medias.

  • By
    MooTools 1.3 Browser Object

    MooTools 1.3 was just released and one of the big additions is the Browser object.  The Browser object is very helpful in that not only do you get information about browser type and browser versions, you can gain information about the user's OS, browser plugins, and...

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!