async then javascript

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();

async function f() { try { let response = await fetch('/no-user-here'); let user = await response.json(); } catch(err) { // catches errors both in fetch and response.json alert(err); } } f();

function resolveAfter2Seconds() { return new Promise(resolve => { setTimeout(() => { resolve('resolved'); }, 2000); }); } async function asyncCall() { console.log('calling'); const result = await resolveAfter2Seconds(); console.log(result); // expected output: 'resolved' } asyncCall();

javscript async await explained

// Promise approach

function getJSON(){

    // To make the function blocking we manually create a Promise.
    return new Promise( function(resolve) {
        axios.get('https://tutorialzine.com/misc/files/example.json')
            .then( function(json) {

                // The data from the request is available in a .then block
                // We return the result using resolve.
                resolve(json);
            });
    });

}

// Async/Await approach

// The async keyword will automatically create a new Promise and return it.
async function getJSONAsync(){

    // The await keyword saves us from having to write a .then() block.
    let json = await axios.get('https://tutorialzine.com/misc/files/example.json');

    // The result of the GET request is available in the json variable.
    // We return it just like in a regular synchronous function.
    return json;
}

Posted by: Guest on November-15-2020

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