Object create define property setter

Question

I need to make it so that every time a specific property on my object is changed - it will call a special method on the same object.

Example:

MyObject.prototype = Object.create({
    specialMethod: function() { /* ... */ }
  }, {
    someValue: {
      set: function(value) {

        /* HOW DO I ASSIGN THE VALUE TO MyObject HERE?*/
        /* I can't do: this.someValue=value, that would create endless recursion */

        this.specialMethod();
      }
    }
  });

How do I assign the value to MyObject within the property setter?

Answer 1

There is no storage place in a getter/setter property, you cannot store values on it. You need to store it somewhere else and create a getter for that. Two solutions:

1. Use a second, "hidden" property:

   MyObject.prototype.specialMethod: function() { /* ... */ };
   Object.defineProperty(MyObject.prototype, "someValue", {
       set: function(value) {
           this._someValue = value;
           this.specialMethod();
       },
       get: function() {
           return this._someValue;
       }
   });
   

2. Use a closure variable (typically created on construction of the instance):

   function MyObject() {
       var value;
       Object.defineProperty(this, "someValue", {
           set: function(v) {
               value = v;
               this.specialMethod();
           },
           get: function() {
               return value;
           }
       });
   }
   MyObject.prototype.specialMethod: function() { /* ... */ };