JavaScript/Notes/Promises: Difference between revisions
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[File:Javascript] | [[File:Javascript]] | ||
Promises are a new addition to ECMAScript. | Promises are a new addition to ECMAScript. | ||
See: http://www.html5rocks.com/en/tutorials/es6/promises/ | See: http://www.html5rocks.com/en/tutorials/es6/promises/ |
Revision as of 22:52, 10 March 2014
File:Javascript 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>