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javascriptv8

javascript multidimensional object

I'm trying to define a multidimensional object in JavaScript with the following code:

function A(one, two) {
    this.one = one;
    this.inner.two = two;
}

A.prototype = {
    one: undefined,
    inner: {
        two: undefined
    }
};
A.prototype.print = function() {
    console.log("one=" + this.one + ", two=" + this.inner.two);
}

var a = new A(10, 20);
var b = new A(30, 40);
a.print();
b.print();

The result is:

one=10, two=40
one=30, two=40

, but I expect

one=10, two=20
one=30, two=40

What am I doing wrong? Is a variable inner a class variable, not an instance?

JavaScript engine: Google V8.

Solution

  • Because the object literal for inner gets shared for all instances. It belongs to the prototype and thus every instance shares the same object. To get around this, you can create a new object literal in the constructor.