Promise delay extension

ext/promise/delay.js

@@ -0,0 +1,38 @@
+// 'delay' - Promise extension
+//
+// promise.delay(timeout)
+//
+// Returns promise that resolves with same value but delayed in time
+
+'use strict';
+
+var nextTick      = require('next-tick')
+  , ensureTimeout = require('timers-ext/valid-timeout')
+  , deferred      = require('../../deferred');
+
+deferred.extend('delay', function (/*timeout*/) {
+	var def, timeout = arguments[0];
+	if (timeout !== undefined) timeout = ensureTimeout(timeout);
+	if (!this.pending) this.pending = [];
+	def = deferred();
+	this.pending.push('delay', [timeout, def.resolve, def.reject]);
+	return def.promise;
+}, function (timeout, resolve, reject) {
+	var delay;
+	if (this.failed) {
+		reject(this.value);
+		return;
+	}
+	if (timeout === undefined) delay = nextTick;
+	else delay = setTimeout;
+	delay(resolve.bind(null, this.value), timeout);
+}, function (/*timeout*/) {
+	var def, timeout = arguments[0], delay;
+	if (timeout !== undefined) timeout = ensureTimeout(timeout);
+	if (this.failed) return this;
+	def = deferred();
+	if (timeout === undefined) delay = nextTick;
+	else delay = setTimeout;
+	delay(def.resolve.bind(def, this.value), timeout);
+	return def.promise;
+});

index.js

@@ -27,6 +27,7 @@ module.exports = assign(require('./deferred'), {
 require('./ext/promise/aside');
 require('./ext/promise/catch');
 require('./ext/promise/cb');
+require('./ext/promise/delay');
 require('./ext/promise/finally');
 require('./ext/promise/get');
 require('./ext/promise/invoke');

test/ext/promise/delay.js

@@ -0,0 +1,14 @@
+'use strict';
+
+var deferred = require('../../../deferred');
+
+module.exports = function (a, d) {
+	var invoked = false, checked = false;
+	deferred(undefined).delay().done(function () {
+		a(checked, true);
+		invoked = true;
+		d();
+	}, d);
+	a(invoked, false);
+	checked = true;
+};