Learning TypeScript 2.x - Second Edition

Asynchronous functions – async and await

Asynchronous functions are a TypeScript feature that arrived with the TypeScript 1.6 release. Developers can use the await keyword to wait for the function results without blocking the normal execution of the program.

Using asynchronous functions helps to increase the readability of a piece of code when compared with the use of promises or callbacks, but technically, we can achieve the same features using both promises and synchronous code.

Let's take a look at a basic async/await example:

let p = Promise.resolve(3); 
 
async function fn(): Promise<number> { 
    let i = await p; // 3 
    return 1 + i; // 4 
} 
 
fn().then((r) => console.log(r)); // 4 

The preceding code snippet declares a promise named p. This promise ...