Then when it's ready, it will receive the results back from the work. The user therefore sits in front of an apparently finished website, but which cannot react to anything if it actually requires JavaScript in the background. The async function is declared using the async keyword. In JavaScript, you can code async tasks in 3 ways. These functions let you work with promises without all of the then and catch syntax and makes your asynchronous code readable. JavaScript environments typically implement this style of programming using callbacks, functions that are called when the actions complete. We can use multiple await statements. We can also define async method as a function Expression –. So the problem that our script wants to access something in the DOM, but at that time it doesn’t even exist, can also occur here. Anyone who tells you differently is either lying or selling something. It doesn’t matter if we include the code within our script tags or if we load an external script at the same place with the script tag that contains the same code — in both cases our console.log returns a “null” — because our h1-tag does not exist yet. The await makes a function asynchronous, so it must be declared as such. Loading external scripts into HTML using the script tag is probably essential. It can happen that the async.js can access the element after all, if there was a delay while loading the script and the browser could already display the h1-tag in the DOM, so that when the async is executed after the delayed loading, the script can successfully access the DOM. Finally async/await will be supported in all major browser soon except IE. Async/Await. JavaScript is a twisty maze of horrible asynchronous calls, all alike. Promises are fine, yet in some situations you may end up with a long chain of then/catch. First of all, we have the async keyword, which you put in front of a function declaration to turn it into an async function.An async function is a function that knows how to expect the possibility of the await keyword being used to invoke asynchronous code.. What does this mean? Adding Async Await. Declaring a function as async will ensure that it always returns a Promise so you don’t have to worry about that anymore. Let’s take a look at some code snippets. Common to both async and defer is that the scripts are loaded in parallel to the construction of the DOM — only when the scripts are executed is different for both. This property reflects the async attribute of the