Class inheritance with method in javascript

Question

I am new to javascript app development.When i came with functions and all i have found a code like

function Parenizor(value) {
console.log(this.setValue());
}

Parenizor.method('setValue', function () {
console.log('am called');
});

Parenizor.method('getValue', function () {
return 1;
});

Parenizor.method('toString', function () {
return 2;
});

And when i called the function like

var a = new Parenizor(1)

a.setValue()

It throws me error like Undefined not a function ..Why is it like this ??..Hope anyone here can find my mistake ..Thanz ..:)

Answer 1

That's not how you define a method. Do it like this:

function K() {}

K.prototype.setValue = function () {};

K.prototype.getValue = function () {};

Answer 2

It seems your code comes from Classical Inheritance in JavaScript , by Douglas Crockford.

I guess you didn't read this part:

To make the examples above work, I wrote four sugar methods. First, the method method, which adds an instance method to a class.

 Function.prototype.method = function (name, func) { this.prototype[name] = func; return this; }; 

Answer 3

Javascript is OO, not with classes, but with prototypes. First when you declare Parenizor, you're declaring a 'constructor'. You probaly want this:

function Parenizor(){
    var value = null;

    this.setValue = function(val){
        value = val;
    };

    this.getValue = function(){
        return value;
    };

    this.toString = function(){
        return String(value);
    };
}

Or also, setting into the object prototype:

function Parenizor(){}
Parenizor.prototype._value = null;
Parenizor.prototype.setValue = function(){...};
Parenizor.prototype.getValue = function(){...};
Parenizor.prototype.toString = function(){...};