JavaScript Asynchronous
JavaScript Async is an important part of writing modern JavaScript code. It allows us to write asynchronous code, which means that we can write code that doesn't block the main thread and can run independently in the background. This is especially important for applications that have to handle a lot of user input, such as web applications.
Async functions are a way of writing asynchronous code in a more manageable way. Async functions are declared with the async keyword, and can be used in place of regular functions. Async functions can be written to take advantage of the event loop, and will wait for certain events to occur before continuing execution.
Let’s take a look at an example of an async function. Here, we have an async function that will fetch data from a server and log it to the console.
async function fetchData(){ let response = await fetch('/data'); let data = await response.json(); console.log(data); }
fetchData();
In this example, the fetchData() function will wait for the server to return its data before logging it to the console. This allows us to write code that handles user input without blocking the main thread.
Async functions can also be used with promises. Promises are a way of handling asynchronous tasks. They allow us to write code that will execute only when certain events occur. For example, we can write a function that will execute after a promise resolves. Here’s an example:
async function fetchData(){ let response = await fetch('/data'); let data = await response.json(); return new Promise((resolve, reject) => { setTimeout(() => { console.log(data); resolve(); }, 1000); }); }
fetchData().then(() => console.log('done!'));