code: function createInput(opt_text) {
      var input = document.createElement('input');
      input.type = 'text';
      input.placeholder = opt_text || '';
      holder.appendChild(input);
      return input;
    }
docs: Creates a text input element and adds it to <body>.
  
  @param {string=} opt_text to use as placeholder
  @return {!HTMLInputElement} added to page