Validate SA Cell Number with Javascript

function validate(){
var MobileNumber = document.getElementById(“MobileNumber”).value;
var MobileNumberRegEx = /^\+27[78][23467][0-9]{7}/;
if (MobileNumberRegEx.test(MobileNumber)) {
return true;
}else{
alert(“Please enter a valid South African mobile phone number\nin the following format: +27820000000″);
return false;
}
}