Check Valid Url JS

function ValidURL(str) {
  var pattern = new RegExp('^(https?:\\//\\//)?'+ // protocol
    '((([a-z\\d]([a-z\\d-]*[a-z\d])*)\\.)+[a-z]{2,}|'+ // domain name
    '((\\d{1,3}\\.){3}\\d{1,3}))'+ // OR ip (v4) address
    '(\\:\d+)?(\\//[-a-z\\d%_.~+]*)*'+ // port and path
    '(\\?[;&a-z\\d%_.~+=-]*)?'+ // query string
    '(\\#[-a-z\\d_]*)?$','i'); // fragment locater
  if(!pattern.test(str)) {
    alert("Please enter a valid URL.");
    return false;
  } else {
    return true;
  }
}

alert("google -> "+ValidURL("www.google.com"));
alert("wrong url -> "+ValidURL("w.goog.c"));