Javascript create date object from mm/dd/yy or dd/mm/yy

try this
dateParts = "dd/mm/yy".split("/");
var date = new Date(dateParts[2], parseInt(dateParts[1]) - 1, dateParts[0]);

or

var date = Date.parse("dd/mm/yy");

or

dateParts = "dd/mm/yy".split("/");
var dateStamp = Date.UTC(dateParts[2], parseInt(dateParts[1]) - 1, dateParts[0]);

that last one converts it to a unix time stamp that you can use in the date methods.