Is there a way to create some type of variable that is the same in every instance of a JavaScript Class (no global variables)?

For example:

function Class(){
  this.foo = 'bar';
  this.setText = setText;
  this.getText = getText;
}

function setText(value){
  this.foo = value;
}

function getText(){
  alert(this.foo);
}

Now I create two instances of the same class like so:

var fruit = new Class();
var groceries = new Class();

When I change the value of foo in the class fruit I also want it to be changed in groceries.

fruit.setText("apple");
fruit.getText(); //alerts apple
groceries.getText(); //SHOULD also alert apple

I am creating the instances of a class dynamically, they don't have a clear variable names (fruit, groceries) like in the example.

Thanks!

Is there a way to create some type of variable that is the same in every instance of a JavaScript Class (no global variables)?

For example:

function Class(){
  this.foo = 'bar';
  this.setText = setText;
  this.getText = getText;
}

function setText(value){
  this.foo = value;
}

function getText(){
  alert(this.foo);
}

Now I create two instances of the same class like so:

var fruit = new Class();
var groceries = new Class();

When I change the value of foo in the class fruit I also want it to be changed in groceries.

fruit.setText("apple");
fruit.getText(); //alerts apple
groceries.getText(); //SHOULD also alert apple

I am creating the instances of a class dynamically, they don't have a clear variable names (fruit, groceries) like in the example.

Thanks!

• javascript
• class
• variables
• object

• 1 possible duplicate of Static variables in JavaScript – asawyer Commented Feb 12, 2014 at 14:31

2 Answers 2

Yes, there absolutely is, just use a property on the function itself:

Class.text = 'apple'

Class.prototype.getText = function () { return Class.text; }
Class.prototype.setText = function (text) { Class.text = text; }

An alternative approach, using a closure:

var Class = (function () {
    var foo = "bar";

    function Class(){
      this.setText = setText;
      this.getText = getText;
    }

    function setText(value){
      foo = value;
    }

    function getText(){
      alert(foo);
    }

    return Class;
}());

var fruit = new Class();
var groceries = new Class();

foo in this case would be similar to a private static property, which is not available from the outside.