on (search, start) {
      'use strict';

      if (search instanceof RegExp) {
        throw TypeError('first argument must not be a RegExp');
      }
      if (start === undefined) { start = 0; }
      return this.indexOf(search, start) !== -1;
    };
  }

  // append
  Document.prototype.append = Element.prototype.append = function append() {
    this.appendChild(_mutation(arguments));
  };
  function _mutation(nodes) {
    if (!nodes.length) {
      throw new Error('DOM Exception 8');
    } else if (nod