Flatten js array without recursion

flatten.js

function flatten(arr) {
  if (!arr || !arr.length) return [];
  
  var nodes = arr.slice();
  var results = [];
  var node = nodes.pop();
  while(node) {
    if (Array.isArray(node)) {
      nodes.push.apply(nodes, node);
    } else {
      results.push(node);
    }
    node = nodes.pop();
  }
  
  return results.reverse();
}