js 生成 GUID

function generateGUID() {
	return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
		var r = Math.random() * 16 | 0,
		v = c === 'x' ? r : (r & 0x3 | 0x8);
		return v.toString(16);
	 });
},