why use async await javascript code example
Example 1: async await
async function showAvatar() {
// read our JSON
let response = await fetch('/article/promise-chaining/user.json');
let user = await response.json();
// read github user
let githubResponse = await fetch(`https://api.github.com/users/${user.name}`);
let githubUser = await githubResponse.json();
// show the avatar
let img = document.createElement('img');
img.src = githubUser.avatar_url;
img.className = "promise-avatar-example";
document.body.append(img);
// wait 3 seconds
await new Promise((resolve, reject) => setTimeout(resolve, 3000));
img.remove();
return githubUser;
}
showAvatar();
Example 2: how to make an async function
function resolveAfter2Seconds() {
return new Promise(resolve => {
setTimeout(() => {
resolve('resolved');
}, 2000);
});
}
//async function:
async function asyncCall() {
console.log('calling');
const result = await resolveAfter2Seconds();
console.log(result);
// expected output: 'resolved'
}
asyncCall();
Example 3: async await
// ASYNC will always returns promises
// NOTE : AWAIT should be kept only inside ASYNC function
// AWAIT can't be used in regular function
/* TIPS : Js is single threaded & synchronous in nature BUT, we can
make it as asyncronous by using (ASYNC/AWAIT)*/
//(Example 1 : fetching Random Image)
async function RandomImage(){ //remember async and await is powerful for async operations, always await should be inside of async only.
try {
const raw_response = await fetch("https://www.themealdb.com/api/json/v1/1/random.php");
if (!raw_response.ok) { // check for the 404 errors
throw new Error(raw_response.status);
}
const json_data = await raw_response.json(); //AWAIT
let data = json_data.meals[0];
console.log(data);
}
catch (error) { // catch block for network errors
console.log(error);
}
}
RandomImage();
//(Example 2 : returning another promise)
console.log("1 is working");
console.log("2 is working");
var AsyncFunction = async() => {
var x = new Promise((resolve,reject) => {
setTimeout(() => resolve("3 is working"), 3000);
});
var result = await x;
return result;
}
AsyncFunction().then(resolved => console.log(resolved));
console.log("3 is working");