JS Async Function via “new Function”
Oct 21, 2021
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!