將此對象綁定到高階函數中的原始對象

Question

在JavaScript中，可以this對象綁定到由高階函數返回的函數嗎？ 下面的代碼示例實質上就是我正在使用的代碼：

var restrict = function(restrictOn, fn) {
   var that = this;

   return function() {
      if (arguments[0] === restrictOn) {
         throw new Error("Condition not met");
      }

      return fn.apply(/*original object*/that, arguments);
   };
};

var MyConstr = function(name) {
   this.name = name;
};
MyConstr.prototype.sayNameWhenNotThree = restrict(3, function() {
   return this.name;
});

var myObj = new MyConstr("Fido");
myObj.sayNameWhenNotThree(3); // Throws error - OK
myObj.sayNameWhenNotThree(5); // SHOULD return "Fido" - does not

在此示例中， restrict()函數正確地傳遞給它正在包裝的函數，但未在myObj函數的上下文中執行。 我曾嘗試過各種this綁定在apply電話，但我想不出如何保留綁定到原來的對象。 能做到干凈嗎？

Answer 1

您需要在內部函數中使用this函數：

var restrict = function(restrictOn, fn) {
   /* at this point this refers to whatever context restrict 
   is called in, in this case - it's window */

   return function() {
      if (arguments[0] === restrictOn) {
         throw new Error("Condition not met");
      }
      /* at this point this refers to the proper target that the returned
      function is being assigned to */
      return fn.apply(this, arguments);
   };
};