Konsul Alfon

callback-vs-promise.js

function ajax(obj) {
    setTimeout(function () {
        obj.success(obj.url);
    }, 100);
}

let x; // 1
ajax({ // 2
    url: "http://google.com",
    success: function(data) {
        x = data;
        console.log("dalam ajax", x);
    }
});
console.log("luar ajax", x); // 3

// CODING KITA (pakai callback)
function loadUrlCallback(callback) {
    ajax({ // 2
        url: "http://google.com",
        success: function(data) {
            callback(data);
        }
    });
}

loadUrlCallback(function (data) {
    console.log("di dalam callback", data);
});

// CODING KITA (pakai promise)
function loadUrlPromise() {
    return new Promise(function (resolve, reject) {
        ajax({ // 2
            url: "http://google.com",
            success: function(data) {
                resolve(data);
            }
        });
    });
}

loadUrlPromise().then(function (data) { // resolver
    console.log("di dalam promise.then", data);
});

// CODING PRO
async function main() {
    let x = await loadUrlPromise(); // tunggu promise nya resolve, masukkan datanya ke x, baru jalankan kode setelahnya
    console.log("dalam async function", x);
}
main();