javascriptprototype-oriented

How to declare a static variable in Javascript

In the following code, I would like to have a counter to keep track of the number of Person objects created. This code is not doing so, how would I accomplish that?

function Person(){
    this.name = "Peter";
    this.counter = this.counter + 1;
    alert(this.counter);
}

Person.prototype.counter = 0;

var p1 = new Person;
var p2 = new Person;
Solution 
  • function Person(){
    this.name = "Peter";
    Person.counter++;
    alert(Person.counter);
}

Person.counter = 0;

var p1 = new Person();
var p2 = new Person();

    Make the "static" variable a property of the Person function, rather than the prototype, and use Person instead of this inside the constructor.

    This is possible because JavaScript functions are first-class (i.e. they are objects), so can have properties of their own.

    Here's a working example of the above code.