JavaScript two lines of code output date time in the specified format

The JavaScript two lines of code output the date time in the specified format, depending on the code:

<summary>
//Format display date time
//</summary>
//<param name= "x" > Date time to display, such as new date () </ Param>
//<param name= "Y" > need to display the format, such as Yyyy-mm-dd hh:mm:ss</param>
function Date2str (x,y) {
    var z ={y:x.getfullyear (), M:x.getmonth () +1,d:x.getdate (), h:x.gethours (), M:x.getminutes (), S:x.getseconds ()};
    Return Y.replace (/(y+| m+|d+|h+|m+|s+)/g,function (v) {return (v.length>1?) 0 ":" ") +eval (' Z. ' +v.slice ( -1))). Slice (-(v.length>2?v.length:2))});
Alert (Date2str (New Date (), "yy-m-d h:m:s"));
Alert (Date2str (New Date (), "yyyy-mm-d h:m:s"));