src/treeview.js
function forEach(arr, callback, scope) {
        var i, len = arr.length;
        for (i = 0; i < len; i += 1) {
          callback.call(scope, arr[i], i);
        }
      }
function forEach(arr, callback, scope) {
        var i, len = arr.length;
        for (i = 0; i < len; i += 1) {
          callback.call(scope, arr[i], i);
        }
      }
A forEach that will work with a NodeList and generic Arrays
@param {array|NodeList} arr The array to iterate over
@param {function} callback Function that executes for each element. First parameter is element, second is index
@param {object} The context to execute callback with