Introduction
In JavaScript, async/await keywords can be used to convert asynchronous operations into synchronous execution. async/await is a new syntax added by ES2017 (also known as ES8), which can make asynchronous requests look like synchronous code, which is more concise and easy to understand.
async is used to declare a function as an asynchronous function, and when the function is executed, a Promise object is returned, indicating the result of the current function execution. The await keyword can be used in the function to wait for the result of the asynchronous operation, and then continue to execute the following code until the asynchronous operation is completed. It should be noted that await can only be used in async functions.
Here is a simple sample code:
async function fetchData() {
const response = await fetch('https://api.example.com/data'); // 等待fetch异步请求完成
const data = await response.json(); // 等待解析JSON数据完成
console.log(data); // 打印获取的数据
}
fetchData(); // 调用异步函数
In the above code, we define an asynchronous function named fetchData, use the await keyword to wait for the fetch request and json parsing operation to complete before printing the obtained data.
It should be noted that although async/await can make asynchronous operations look like synchronous code, it does not really turn asynchronous code into synchronous execution, and the program is still asynchronous during execution. In addition, using async/await requires attention to error handling, and you can use try/catch statements to catch exceptions.