Should one use setter/getter methods in JavaScript

Question

First things first, this may be primary opinion based, so I'm looking for technical reasons and commonly accepted best practices to do one or the other thing.

If I write a "Class" and create a member of it, I can access the instance properties like this

function MyClass(){

  var self = this;

  self.foo = 'bar'

}   

var instance = new MyClass();

instance.foo = '420';

I could, however, also create a method to set the property, so that there is no knowledge about the internal structure of the class needed

MyClass.prototype.setFoo = function(prop){
  this.foo = prop;
};

Considering professional development, is there a reason to prefer one variant over the other?

Basically the list from [why use getters/setters](http://stackoverflow.com/q/1568091/1048572) is valid for JS as well. — Bergi, May 21 '14 at 09:15

score 5 · Answer 1 · answered May 21 '14 at 06:33

5

Here's a good example of how to use a private correctly - using scopes(in your example I can set\access foo outside the function without going through the set\get functions):

function MyClass(){
    var foo = 'bar'; // private because of "scope"

    this.setfoo  = function(f) {
        foo = f;
    }

    this.getfoo = function() {
        return foo;
    }
}   

var instance = new MyClass();
console.log(instance.foo); // undefined
console.log(instance.getfoo()); // bar
instance.setfoo('a');
console.log(instance.getfoo()); // a

Here's a Fiddle

answered May 21 '14 at 06:33

Amir Popovich

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Thank you. This sample leads me to a related question: Why are you implementing those setter methods as static ones instead of adding them to the prototype? – Wottensprels May 21 '14 at 06:43
1

@Sprotte Because a prototype function wouldn't have access to the privately scoped variable. – deceze May 21 '14 at 07:03
When you make 'private' members with closures you need separate method instances for each object instance. Each method instance will only see it's own object's private vars. – Vatev May 21 '14 at 07:03
1

Here's a good stack post that will give you answers: http://stackoverflow.com/questions/436120/javascript-accessing-private-member-variables-from-prototype-defined-functions – Amir Popovich May 21 '14 at 07:28

score 0 · Answer 2 · answered May 21 '14 at 08:38

I suggest you read Nicholas Zakas's Professional Java Script for Web Developpers, starting page 90. He explains quite clearly the different patterns (Factory vs Constructor vs Prototype) to create a 'Class' in Java Script.

I got all the info I needed when I tried to create some classes a while ago. I hope you find what need :)

The problem with Amiros's suggestion is that, as Nicholas Zakas explains, "every time the myClass() function is called, a new function is created called setFoo(), meaning that every object has its own version of setFoo() when, in reality, each object should share the same function.

For example,

class1 = new MyClass();
class2 = new MyClass();
console.log(class1.setFoo == class2.setFoo); // false

Thank you, I'll give it a try! The problem with the prototype pattern is, as Amiros pointed out, that properties will still be editable from outside. Now I can't decide what way to go :/ — Wottensprels, May 21 '14 at 08:41
What does Nicholas Zakas say about setter/getter methods? OP did not ask about classes. — Bergi, May 21 '14 at 09:06

Should one use setter/getter methods in JavaScript

2 Answers2