How to validate validation in cliient side in java script

function chkValidation(nextTab)
{
if (tab.name=='EmployeeDetails')
{
var btnSave = document.getElementById("<%=btnSave.clientID%>");
WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions('ctl00$ContentPlaceHolder1$btnSave', '', true, '', '', false, false));
if (Page_ClientValidate()==false)
return false;
}
else
{
tab.name = nextTab;
}
}