JavaScript/Notes/Promises

Promises are a new addition to ECMAScript. See: http://www.html5rocks.com/en/tutorials/es6/promises/ https://people.mozilla.org/~jorendorff/es6-draft.html#sec-promise-objects

Example with no Promise

<source lang="javascript"> var img = new Image();

var rejectTimer = setTimeout( function() {

 reject(Error("It broke"));

}, 4 * 1000);

img.onload = function() { clearTimeout(rejectTimer); resolve("Stuff worked!"); };

img.src = "https://www.google.com/images/srpr/logo11w.png?res";

function resolve(msg) {

	console.log(msg);

} function reject(err) {

 console.error(err);

};

</source>

Example with Promise

<source lang="javascript"> var promise = new Promise(function(resolve, reject) {

 var img = new Image();

 var rejectTimer = setTimeout( function() {
   reject(Error("It broke"));
 }, 4 * 1000);

 img.onload = function() {
 	clearTimeout(rejectTimer);
 	resolve("Stuff worked!");
 }
 img.src = "https://www.google.com/images/srpr/logo11w.png?sss";

});

promise.then(

function(msg) { 
	console.log(msg);
}, 
function(err) {
   console.error(err);

}); </source>