Validate Phone Number

SAMPLE CODE
 
  
 <script>
 
 <SCRIPT type="text/javascript"  >
 function valPhoneNumber(){
 
  var varInput = frmGetNumber.theinput.value;
	
	var varError = 'n';
 		 
			 if (varInput.length !== 8) {
			 alert("The length must be 8 characters");
			  varError = 'y';
				 }
				 
			 for (var i = 0; i < varInput.length; i++) {
			  if (i === 3) {  // if statement 1
				 if (varInput.charAt(i) !== '-') { // if statement 2
				 alert("The 3rd character must be a dash");
				  varError = 'y';
					} // end if statement 2
				} else if (isNaN(varInput.charAt(i))) {
				 alert("All numbers must be numeric");
				 varError = 'y';
				} // if statement 1
				
			} // end for statement
			 
			if (varError === 'n') {
			 alert("Valid Phone Number")
			}
			 
    	 }
			 
			
</script>

Enter the phone number (xxx-xxxx)<input type="text" value="" name="theinput" size="8" maxlength="8" > <br><br><br>

</form>