timwienk/promise.js

Very simple but complete Promise implementation.

Promise.js

Very simple but complete Promise implementation.

• Implements the Promises/A+ 1.1.0 specification:
  • Promise.prototype.then(onResolve, onReject).
• Implements the ES6 Promise draft:
  • new Promise(function(resolve, reject){}),
  • Promise.all(iterable),
  • Promise.race(iterable),
  • Promise.reject(reason),
  • Promise.resolve(value),
  • Promise.prototype.catch(onReject).
• Implements some of the earlier proposed features for Promises/A:
  • Promise.prototype.get(propertyName),
  • Promise.prototype.call(methodName),
  • Third optional argument onProgress to then:
    • Promise.prototype.then(onResolve, onReject, onProgress).
• And to actually be able to use the progress handler:
  • Third argument progress for the executor function passed to new Promise:
    • new Promise(function(resolve, reject, progress){}).
• Tests against the Promises/A+ tests as well as some "local" tests (most of which are adapted copies if tests found in domenic/promises-unwrapping) for the functionality that's not part of Promises/A+.

Example

function get(url){
	var promise = new Promise(function(resolve, reject, progress){
		var request = new XMLHttpRequest();

		request.addEventListener('load', function(){
			if (request.status == 200){
				resolve(request.response);
			} else {
				reject(new Error(request.statusText));
			}
		}, false);

		request.addEventListener('progress', progress, false);
		request.addEventListener('error', reject, false);
		request.addEventListener('abort', reject, false);

		request.open('GET', url, true);
		request.send();
	});
	return promise;
}

get('/some/path').then(
	function(response){
		console.log(response);
	},
	function(reason){
		console.log(reason);
	},
	function(event){
		console.log(event);
	}
);