Javascript form validate

function checkFields() {
		var ok = true;
		var errStr = "Please fill the following fields correctly: \n";
		if($('#contactForm #name').val() == 'Name') {
			ok = false; 
			errStr += 'Name \n';
		}
		if(isValidEmail($('#contactForm #mdrlyj-mdrlyj').val()) == false) {
			ok = false; 
			errStr += 'Email Address \n';
		}
		if($('#contactForm #cm-f-olrllh').val() == 'Company Name') {
			ok = false;
			errStr += 'Company Name \n';
		}
 
		if(!isValidPostcode($('#contactForm #Postcode').val())) {
			ok = false;
			errStr += 'Postcode \n';
		}
		if(!ok) {
			alert(errStr);
		} else {
			submitform('#contactForm');
		}
	}
 
	function isValidEmail(email) {
 	  	var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
   		var address = email;
   		if(reg.test(address) == false) {
   	   		return false;
   		} else {
   			return true;
   		}
	}
	function isValidPostcode(p) {
		var postcodeRegEx = /[A-Z]{1,2}[0-9]{1,2} ?[0-9][A-Z]{2}/i;
		return postcodeRegEx.test(p);
	}