promise、async await

`Promise` is a built-in JavaScript object that represents a value that may not be available yet but will be resolved in the future. It is commonly used for asynchronous operations, such as fetching data from a server or reading a file from disk. Promises have three states: pending, resolved, or rejected.

`async/await` is a syntax for working with Promises that was introduced in ECMAScript 2017. The `async` keyword is used to define an asynchronous function that returns a Promise. The `await` keyword is used to pause the execution of the function until a Promise is resolved. This allows for more readable and concise code when working with asynchronous operations.

Here is an example of using Promise and async/await:

Promise:

fetch('https://example.com/data')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error(error));

async/await:

async function fetchData() {
  try {
    const response = await fetch('https://example.com/data');
    const data = await response.json();
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}

fetchData();