Provide a fallback if webworkers do not exist

Fixes #30.

Author: Sebmaster

lib/parallel.js

@@ -69,7 +69,8 @@
 	var defaults = {
 		ie10shim: !isNode,
 		path: (isNode ? __dirname + '/' : 'lib/') + 'eval.js',
-		maxWorkers: isNode ? require('os').cpus().length : 4
+		maxWorkers: isNode ? require('os').cpus().length : 4,
+		synchronous: true
 	};
 
 	function Parallel(data, options) {
@@ -120,6 +121,10 @@
 			wrk = new Worker(this.options.path);
 			wrk.postMessage(src);
 		} else {
+			if (Worker === undefined) {
+				return undefined;
+			}
+
 			try {
 				if (this.requiredScripts.length !== 0) {
 					if (this.options.ie10shim) {
@@ -152,12 +157,21 @@
 		var newOp = new Operation();
 		this.operation.then(function () {
 			var wrk = that._spawnWorker(cb);
-			wrk.onmessage = function (msg) {
-				wrk.terminate();
-				that.data = msg.data;
-				newOp.resolve(null, that.data);
-			};
-			wrk.postMessage(that.data);
+			if (wrk !== undefined) {
+				wrk.onmessage = function (msg) {
+					wrk.terminate();
+					that.data = msg.data;
+					newOp.resolve(null, that.data);
+				};
+				wrk.postMessage(that.data);
+			} else if (that.options.synchronous) {
+				setImmediate(function () {
+					that.data = cb(that.data);
+					newOp.resolve(null, that.data);
+				});
+			} else {
+				throw new Error('Workers do not exist and synchronous operation not allowed!');
+			}
 		});
 		this.operation = newOp;
 		return this;
@@ -166,12 +180,21 @@
 	Parallel.prototype._spawnMapWorker = function (i, cb, done) {
 		var that = this;
 		var wrk = that._spawnWorker(cb);
-		wrk.onmessage = function (msg) {
-			wrk.terminate();
-			that.data[i] = msg.data;
-			done();
-		};
-		wrk.postMessage(that.data[i]);
+		if (wrk !== undefined) {
+			wrk.onmessage = function (msg) {
+				wrk.terminate();
+				that.data[i] = msg.data;
+				done();
+			};
+			wrk.postMessage(that.data[i]);
+		} else if (that.options.synchronous) {
+			setImmediate(function () {
+				that.data[i] = cb(that.data[i]);
+				done();
+			});
+		} else {
+			throw new Error('Workers do not exist and synchronous operation not allowed!');
+		}
 	};
 
 	Parallel.prototype.map = function (cb) {
@@ -203,12 +226,21 @@
 	Parallel.prototype._spawnReduceWorker = function (data, cb, done) {
 		var that = this;
 		var wrk = that._spawnWorker(cb);
-		wrk.onmessage = function (msg) {
-			wrk.terminate();
-			that.data[that.data.length] = msg.data;
-			done();
-		};
-		wrk.postMessage(data);
+		if (wrk !== undefined) {
+			wrk.onmessage = function (msg) {
+				wrk.terminate();
+				that.data[that.data.length] = msg.data;
+				done();
+			};
+			wrk.postMessage(data);
+		} else if (that.options.synchronous) {
+			setImmediate(function () {
+				that.data[that.data.length] = cb(data);
+				done();
+			});
+		} else {
+			throw new Error('Workers do not exist and synchronous operation not allowed!');
+		}
 	};
 
 	Parallel.prototype.reduce = function (cb) {