How to use JQuery Custom validation method to validate phone number

How to use JQuery Custom validation method to validate phone number

I wanted to validate a phone number using jQuery custom validation method.I tried to write a method for that but it didn't work .Can anyone help me to find the error of this code .As I'm new to this language I don't know much about jQuery. here is my code


  2. $(document).ready(function () {

  4. jQuery.validator.addMethod('phonenu', function(value, element) {
  5.     if(element.value != 10 && element.value == isNaN)
  6.     {
  7.         return false;
  8.     }
  9.     else 
  10.     {    return true;
  11.         
  12.     }, 'Invalid phone number'}); 


  15.     $('#myform').validate({
  16.         rules: {
  17.             phone: {
  18.                 required: true
  19.                 phonenu: true,
  20.                 
  21.             }
  22.         }
  23.     });

  25. });
html code 
  2. <form id="myform">
  3.     <input name="phone" type="text" />
  4.     <input type="submit" />
  5. </form>