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
    Cross Browser CSS Box Shadows

    Box shadows have been used on the web for quite a while, but they weren't created with CSS -- we needed to utilize some Photoshop game to create them.  For someone with no design talent, a.k.a me, the need to use Photoshop sucked.  Just because we...

  • By
    Reverse Element Order with CSS Flexbox

    CSS is becoming more and more powerful these days, almost to the point where the order of HTML elements output to the page no longer matters from a display standpoint -- CSS lets you do so much that almost any layout, large or small, is possible.  Semantics...

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!