UUID（通用唯一識别碼）生成方法

uuid: function() {
	   var s = [];
	    var hexDigits = "0123456789abcdefghijklmnopqrstuvwxyz";
	    for (var i = 0; i < 36; i++) {
	        s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
	    }
	    s[14] = "4"; // bits 12-15 of the time_hi_and_version field to 0010
	    s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1); // bits 6-7 of the clock_seq_hi_and_reserved to 01
	    s[8] = s[13] = s[18] = s[23] = "-";
	
	    var uuid = s.join("");
	    return uuid;
	}