#javascript #promise example based on Mozilla Developer Network documentation

promises.js

/*jslint devel: true, browser: true, es5: true */
/*global Promise */

var promiseCount = 0;

function testPromise() {
    'use strict';
    
    promiseCount += 1;
    var thisPromiseCount = promiseCount;

    console.log(thisPromiseCount + ') Started (Sync code started)');
    
    // We make a new promise: we promise the string 'result' (after waiting 3s)
    var p1 = new Promise(
        // The resolver function is called with the ability to resolve or reject the promise
        function (resolve, reject) {
            console.log(thisPromiseCount + ') Promise started (Async code started)');
            // This is only an example to create asynchronism
            window.setTimeout(
                function () {
                    // We fulfill the promise !
                    resolve(thisPromiseCount);
                },
                Math.random() * 2000 + 1000
            );
        }
    );

    // We define what to do when the promise is resolved/fulfilled with the then() call,
    // and the catch() method defines what to do if the promise is rejected.
    p1
        .then(function (val) {
            // Log the fulfillment value
            console.log(val + ') Promise fulfilled (Async code terminated)');
        })
        .catch(function (reason) {
            // Log the rejection reason
            console.log('Handle rejected promise (' + reason + ') here.');
        });

    console.log(thisPromiseCount + ') Promise made (Sync code terminated)');
}