promise polyfill

promise/promise.js

@@ -0,0 +1,74 @@
+"use strict"
+
+function Promise(executor) {
+	if (!(this instanceof Promise)) throw new Error("Promise must be called with `new`")
+	if (typeof executor !== "function") throw new Error("executor must be a function")
+	
+	var self = this, resolvers = [], rejectors = [], resolveCurrent = handler(resolvers, true), rejectCurrent = handler(rejectors, false)
+	function handler(list, shouldAbsorb) {
+		return function execute(value) {
+			if (shouldAbsorb && (typeof value === "object" || typeof value === "function") && typeof value.then === "function") {
+				if (value === self) rejectCurrent(new Error("Promise cannot be resolved with itself"))
+				value.then(execute, rejectCurrent)
+			}
+			else {
+				setTimeout(function() {
+					for (var i = 0; i < list.length; i++) list[i](value)
+					resolvers.length = 0, rejectors.length = 0
+				}, 0)
+			}
+		}
+	}
+	
+	this._instance = {resolvers: resolvers, rejectors: rejectors}
+	try {executor(resolveCurrent, rejectCurrent)} catch (e) {rejectCurrent(e)}
+}
+Promise.prototype.then = function(onFulfilled, onRejection) {
+	function handle(callback, list) {
+		if (typeof callback === "function") {
+			list.push(function(value) {
+				try {resolveNext(callback(value))} catch (e) {if (rejectNext) rejectNext(e)}
+			})
+		}
+	}
+	var resolveNext, rejectNext
+	handle(onFulfilled, this._instance.resolvers), handle(onRejection, this._instance.rejectors)
+	return new Promise(function(resolve, reject) {resolveNext = resolve, rejectNext = reject})
+}
+Promise.prototype.catch = function(onRejection) {
+	return this.then(null, onRejection)
+}
+Promise.resolve = function(value) {
+	if (value instanceof Promise) return value
+	return new Promise(function(resolve, reject) {resolve(value)})
+}
+Promise.reject = function(value) {
+	return new Promise(function(resolve, reject) {reject(value)})
+}
+Promise.all = function(list) {
+	return new Promise(function(resolve, reject) {
+		var total = list.length, count = 0, values = []
+		for (var i = 0; i < list.length; i++) {
+			new function(i) {
+				function consume(value) {
+					count++
+					values[i] = value
+					if (count === total) resolve(values)
+				}
+				if ((typeof list[i] === "object" || typeof list[i] === "function") && typeof list[i].then === "function") {
+					list[i].then(consume, reject)
+				}
+				else consume(list[i])
+			}(i)
+		}
+	})
+}
+Promise.race = function(list) {
+	return new Promise(function(resolve, reject) {
+		for (var i = 0; i < list.length; i++) {
+			list[i].then(resolve, reject)
+		}
+	})
+}
+
+module.exports = Promise