Solution
First get the Date and then try with Slashes for formatting.
Code
var date = new Date();
var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);
var lastDayWithSlashes = (lastDay.getDate()) + '/' + (lastDay.getMonth() + 1) + '/' + lastDay.getFullYear();
alert(lastDayWithSlashes);
Demo
[Demo] Get last date of the current month in jQuery[
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