Phone number validation js

// Phone number validation
/*It validates the phone number in international level. The argument PhoenNumber is the id of textbox. PhoneNumber
must contain a minimum of 10 digits. checkRequired defines that it is either optional or must. */
function ValidatePhoneNumber(PhoneNumber, checkRequired)
{
var Phone = PhoneNumber.value;
if(checkRequired == true)
{
if (Phone == null Phone == "" Phone == '')
{
alert("Please Enter your Phone Number")
PhoneNumber.select();
PhoneNumber.focus();
return false;
}
}
else
{
if(Phone == null Phone == '' Phone == "")
{
return true;
}
}
if (checkInternationalPhone(Phone) == false)
{
alert("Please Enter a Valid Phone Number");
PhoneNumber.select();
PhoneNumber.focus();
return false;
}
return true;
}