Create an array of a parents children in javascript

Question

I am trying to create an array of a parent div's (id="lol") children and them fetch them to change display:none; except for the child with id="a". I've tried this but it doesn't work. How can I improve this to get it to work?

function myFunction() {

  var x = document.getElementById('a');

  var children = [].slice.call(document.getElementById('lol').getElementsByTagName('*'),0);
  var arrayLength = children.length;          

  for (var i = 0; i < arrayLength; i++) {
    var name = children[i].getAttribute('id');
    var z = document.getElementById(name);
    z.style.display = 'none';
  }
  x.style.display = 'block';
} 

Answer 1

If every child has an id attribute than it will work. Otherwise, some children might not have id attribute, in that case variable z will be undefined and accessing style property over z which is undefined will give error. Simple fix would be just handling undefined variable:

   if(z)      
       z.style.display = 'none';

Same goes with variable x, too.