Syntax for async arrow function


I can mark a javascript function as "async" (i.e. returning a promise) with the async keyword. Like this:

async function foo() {
  // do something
}

What is the equivalent syntax for arrow functions?

Async arrow functions look like this:

const foo = async () => {
  // do something
}

Async arrow functions look like this for a single argument passed to it:

const foo = async evt => {
  // do something with evt
}

The anonymous form works as well:

const foo = async function() {
  // do something
}

An async function declaration looks like this:

async function foo() {
  // do something
}

Using async function in a callback:

const foo = event.onCall(async () => {
  // do something
})

This the simplest way to assign an async arrow function expression to a named variable:

const foo = async () => {
  // do something
}

(Note that this is not strictly equivalent to async function foo() { }. Besides the differences between the function keyword and an arrow expression, the function in this answer is not "hoisted to the top".)


Immediately Invoked Async Arrow Function:

(async () => {
    console.log(await asyncFunction());
})();

Immediately Invoked Async Function Expression:

(async function () {
    console.log(await asyncFunction());
})();

Async Arrow function syntax with parameters

const myFunction = async (a, b, c) => {
   // Code here
}

You may also do:

 YourAsyncFunctionName = async (value) => {

    /* Code goes here */

}

Basic Example

folder = async () => {
    let fold = await getFold();
    //await localStorage.save('folder');
    return fold;
  };