要变成这样

代码如下

(function($) {
  $.fn.caret = function(index){
    if (typeof index === "undefined"){
      return this[0].selectionStart;
    } else {
      this[0].focus();
      return this[0].setSelectionRange(index, index);
    }
  }
  $.fn.caretSelection = function(start, end){
    if (typeof start === "undefined" && typeof end === "undefined"){
      return [this[0].selectionStart, this[0].selectionEnd];
    } else {
      this[0].focus();
      return this[0].setSelectionRange(start, end);
    }
  }
})(jQuery);