CODEWITHSUNDEEP
javascript
knikolov
knikolov

Reputation: 1800

Uncaught TypeError: Object function has no method

The idea is to implement the calculateSurface method from Shape on the inherited class Rectangle, and calculate the surface with the parameters passed on the Rectangle class.

function Shape (w,h){
    this.h = h;
    this.w = w;
    this.calculateSurface = function (){
        return this.w*this.h;
    };
}

function Rectangle (w,h){
    Shape.apply(this, arguments);
    this.w = w;
    this.h = h;
    this.calcSurface = function(){
        return Shape.calculateSurface(this.w, this.h);
    };
}

Rectangle.prototype = new Shape();
Rectangle.prototype.constructor = Rectangle;

var rec = new Rectangle(4,4);

console.log(rec.calcSurface());

The error I get is:

    Uncaught TypeError: Object function Shape(w,h){
    this.h = h;
    this.w = w;
    this.calculateSurface = function (){
        return this.w*this.h;
    };
} has no method 'calculateSurface'

Upvotes: 0

Views: 2740

Answers (3)

happyCoda
happyCoda

Reputation: 418

Use this instead: 

return (new Shape(this.w, this.h)).calculateSurface(this.w, this.h);

Upvotes: 0

Clyde Lobo
Clyde Lobo

Reputation: 9174

Change

return Shape.calculateSurface(this.w, this.h);

to

return this.calculateSurface(this.w, this.h);

Because you are pointing Rectangle's Prototype to Shape's in

Rectangle.prototype = new Shape();

Upvotes: 0

alex
alex

Reputation: 490607

This line...

return Shape.calculateSurface(this.w, this.h);

Is looking for a calculateSurface() method on your Shape() function. Except it's not there, it's on the object returned by the constructor.

You want something like this...

var self = this;
this.calcSurface = function(){
    return self.calculateSurface(this.w, this.h);
};

jsFiddle.

Also, it may be worth placing calculateSurface() on Shape's prototype property, that way if you create lots of Shape objects, you only have the method living once in memory.

Upvotes: 2

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