The Async Constructor

The Problem

You want to run some asynchronous code in your class constructor. You wisely believe that adding async before the word constructor will work, as shown below (figure 1).

Figure 1 - async constructor (not working)

class GoogleClass {
    async constructor() {
            const response = await fetch('https://www.google.com');
            ...some logic;
    }
}

Alas, your class fails to build, you get an error: Uncaught SyntaxError: Class constructor may not be an async method.

The Solution

So there is a really simple solution, return a function in the constructor, i.e. a closure. In this case (figure 2), we create an anonymous async function, that we instantly return on newing up the class with the new operator.

Figure 2 - async constructor (working)

class GoogleClass {
    constructor() {
        return (async () => {
                    const response = await fetch('https://www.google.com');
                    ...some logic;
                    })();
        }
    }
}