While solving problem I got error after writing code: chrome headless Alert function function should generate a alert FAILED TypeError: Cannot read property 'value' of null please help to solve this.

I tried the following code:

function runlist(){

  var name=document.getElementById("myname").value;
  var phone=document.getElementById("myphone").value;
  var country=document.getElementById("mycountry").value;
  var email=document.getElementById("mymail").value;
  var result = name + ','+phone+','+country+','+email;

  alert(result);  
  return result;
}