this._super()

https://learn.jquery.com/jquery-ui/widget-factory/extending-widgets/

https://api.jqueryui.com/jquery.widget/#method-_super

https://johnresig.com/blog/simple-javascript-inheritance/

To make the parent's methods available, the widget factory provides two methods - _super() and _superApply().

Using _super() and _superApply() to Access Parents

https://learn.jquery.com/jquery-ui/widget-factory/extending-widgets/#using-_super-and-_superapply-to-access-parents

_super() and _superApply() invoke methods of the same name in the parent widget. Refer to the following example. Like the previous one, this example also overrides the open() method to log "open". However, this time _super() is run to invoke dialog's open() and open the dialog.

$.widget( "custom.superDialog", $.ui.dialog, {
    open: function() {
        console.log( "open" );
 
        // Invoke the parent widget's open().
        return this._super();
    }
});
 
$( "<div>" ).superDialog();

proxiedPrototype[ prop ] = (function() {
   var _super = function() {
         return base.prototype[ prop ].apply( this, arguments );
      },
      _superApply = function( args ) {
         return base.prototype[ prop ].apply( this, args );
      };
   return function() {
      var __super = this._super,
         __superApply = this._superApply,
         returnValue;

      this._super = _super;
      this._superApply = _superApply;

      returnValue = value.apply( this, arguments );

      this._super = __super;
      this._superApply = __superApply;

      return returnValue;
   };
})();

jquery ui widget 源码分析

 //在传入的ui原型中有方法调用this._super 和this.__superApply会调用到base上（最基类上）的方法
127         $.each(prototype, function(prop, value) {
128             //如果val不是function 则直接给对象赋值字符串
129             if (!$.isFunction(value)) {
130                 proxiedPrototype[prop] = value;
131                 return;
132             }
133             //如果val是function
134             proxiedPrototype[prop] = (function() {
135                 //两种调用父类函数的方法
136                 var _super = function() {
137                         //将当期实例调用父类的方法
138                         return base.prototype[prop].apply(this, arguments);
139                     },
140                     _superApply = function(args) {
141                         return base.prototype[prop].apply(this, args);
142                     };
143                 return function() {
144                     var __super = this._super,
145                         __superApply = this._superApply,
146                         returnValue;
147                     //                console.log(prop, value,this,this._super,'===')
148                     //                debugger;
149                     //在这里调用父类的函数
150                     this._super = _super;
151                     this._superApply = _superApply;
152  
153                     returnValue = value.apply(this, arguments);
154  
155                     this._super = __super;
156                     this._superApply = __superApply;
157                     //                console.log(this,value,returnValue,prop,'===')
158                     return returnValue;
159                 };
160             })();
161         });