JavaScript 2022 - New Features - Part 4

Top level await operator

The await operator was added in ES8(ECMAScript 2018) it pauses the execution until a promise is completed or rejected.

With ES13 the await operator can be used in global scope.

// await with function - toplevel
// Awaiting a promise to be fulfilled
function resolveAfter2Seconds(x) {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve(x);
        }, 1000);
    });
}

await resolveAfter2Seconds(10).then(
        arg => {console.log("then",arg);}
    );

In the above code the await operator is used

• With a standard function (non async)

• In a global context

When the function's promise is completed the then() function is called which prints the value 10.

The await operator can also be used for loading modules

//mymath.mjs
export function add(a,b) {
    return a+b;
}


// program.js
  let module;
    try {
        module = await import('./mymath.mjs');
        console.log("Module loaded", module);
    } catch {
        console.log("error")
    }

In the above code module mymath.mjs is loaded using await keyword