Here is a solution that is about as simple as your recursive solution. (8 lines of code.)

  function walkDOM2(n) {
    var stack = [n];
    while (stack.length > 0) {
      var node = stack.pop();
      console.log(node);
      stack = stack.concat(Array.prototype.slice.call(node.childNodes, 0).reverse());
    }
  }

Some notes on the above:

• After you pop an item off the end of the stack, you replace it with it's children.
• The children are reversed so that the first child is placed at the end of the stack, so it will be the next node to be popped.
• Use Array.prototype.slice.call() to turn the childNodes NodeList into an Array so it can be added to the stack with concat.
• There is no hasChildNodes() check, but sometimes there will be no child nodes and an empty array will be added to the stack.

Here is a solution that is about as concise as your recursive solution. (8 lines of code.)

  function walkDOM2(n) {
    var stack = [n];
    while (stack.length > 0) {
      var node = stack.pop();
      console.log(node);
      stack = stack.concat(Array.prototype.slice.call(node.childNodes, 0).reverse());
    }
  }

Some notes on the above:

• After you pop an item off the end of the stack, you replace it with it's children.
• The children are reversed so that the first child is placed at the end of the stack, so it will be the next node to be popped.
• Use Array.prototype.slice.call() to turn the childNodes NodeList into an Array so it can be added to the stack with concat.
• There is no hasChildNodes() check, but sometimes there will be no child nodes and an empty array will be added to the stack.