Creating multiple properties with the same getters and setters

Question

Problem

I recently wrote some JavaScript program that includes the use of getters and setters . I read the MDN documentation for both methods, but I got confused trying to use them.

In a nutshell, I just want to create a series of similar properties that will have the same getters and setters , but I do not want to rewrite each setter and getter for each property.

Implementation

The above, I tried to execute the following code:

var defaultProperty = { set: function(val) { this.value = val - 1; // Just an example }, get: function() { return this.value + 1; // Just an example } }; var myObj = {}; Object.defineProperties(myObj, { foo: defaultProperty, bar: defaultProperty }); 

Then I assigned new values ​​to my foo and bar properties, for example:

 myObj.foo = 3; myObj.bar = 7; 

And finally, I was expecting something like this :

 console.log(myObj.foo, myObj.bar); > 3 7 

But I unexpectedly got this instead :

 > 7 7 

It seems that both properties apply to either the same memory address or the same setters / receivers. Noticed this, I tried to solve the problem and created each property separately, for example:

 Object.defineProperties(myObj, { foo: { set: function(val) { this.value = val - 1; }, get: function() { return this.value + 1; } }, bar: { set: function(val) { this.value = val - 1; }, get: function() { return this.value + 1; } } }); 

But the result was the same:

 myObj.foo = 3; myObj.bar = 7; console.log(myObj.foo, myObj.bar); > 7 7 

I also tried using the __defineSetter__ and __defineGetter__ , but the result did not change.

My questions

Now, after several unsuccessful attempts to solve my problems, I wonder:

• Is it possible to define the same setters and getters for different properties of an object?
• If so, what am I doing wrong, and why do my properties behave as if they are the same property?
• Is there a better way to accomplish what I'm trying to do (perhaps without writing each setter and getter for each property)?

Answer 1

Is it possible to define the same setters and getters with different properties of an object?

Yes, although this is not recommended, as you can see from your experience.

what am I doing wrong, and why do my properties behave as if they are the same property?

Since they store / get the available value that was set / received, it is always stored in the same .value property on your object: myObj.value == 6 , so both myObj.foo and myObj.bar give 7 .

Is there a better way to accomplish what I'm trying to do?

Save the values ​​in the variables of the closing area and use the function to define the properties:

 function makeDefaultProperty(obj, name) { var value; return Object.defineProperty(obj, name, { set: function(val) { value = val - 1; // Just an example }, get: function() { return value + 1; // Just an example } }); }; var myObj = {}; makeDefaultProperty(myObj, "foo"); makeDefaultProperty(myObj, "bar"); 

Of course, instead of a local variable, you can simply use different "internal" properties, and you can also use a different way to create shared setters / getters using a function. Both apply:

 function defaultProperty(name) { return { set: function(val) { this[name] = val - 1; // Just an example }, get: function() { return this[name] + 1; // Just an example } }; } var myObj = Object.defineProperties({}, { foo: defaultProperty("_foo"), bar: defaultProperty("_bar") });