I Could Not Run My Method -JavaScript

Question

first of all I am new at learning coding. In my code I wanted to create a function "Square" which creates a square object by using the length parameter that you passed in.And another function to calculate its perimeter.Here is my code and I could not find my fault can you help me ?

function Square(length){
    this.length = length;
}

var calcPerimeter = function() {
  return this.sideLength * 4;
};
var calcArea = function() {
    return this.sideLength * this.sideLength ;
};

var p = square.calcPerimeter();
var a = square.calcArea();

var calcPerimeter2 = function(n){
    return n*4;
 };
var square1 = new Square(5);
square1.calcPerimeter2();

I'd take a step back and maybe spin through some JS tutorials; functions you define in the global scope don't magically become functions on objects. What's `square` that you're trying to call them on? — Dave Newton, Nov 27 '14 at 18:04
I wanted to create a Constructor which name is Square. And when i write "var square1 = new Square(2);" it would create a new square which has 2 as length. — Recomer, Nov 27 '14 at 18:07
The following answer may be helpful, it explains prototype, constructors, inheritance, mix ins and more: http://stackoverflow.com/questions/16063394/prototypical-inheritance-writing-up/16063711#16063711 — HMR, Nov 28 '14 at 00:40

score 1 · Accepted Answer · answered Nov 27 '14 at 18:30

1

Maybe this is what your looking for:

function Square(length){
    this.sideLength = length;
}

Square.prototype.calcPerimeter = function() {
  return this.sideLength * 4;
};
Square.prototype.calcArea = function() {
    return this.sideLength * this.sideLength ;
};

var square = new Square(5);

console.log(square.calcPerimeter());
console.log(square.calcArea());

answered Nov 27 '14 at 18:30

CD..

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Thank you very much! It was exactly what I was trying to do.So what does prototype do ?Why do you use it ? – Recomer Nov 27 '14 at 18:33
have a look: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/prototype – CD.. Nov 27 '14 at 18:34

score 1 · Answer 2 · answered Nov 27 '14 at 21:32

1

Try this...

    function Square(length){
     this.length = length; //Constructor
    }

    Square.prototype.calcPerimeter = function(){
      return this.length * 4;
    }

    Square.prototype.calcArea = function() {
      return this.length * this.length;
    }

   var s = new Square(5);
   s.calcPerimeter();

Using this pattern you can simulate inheritance in javascript, this pattern is called "Prototype". Hope this work for you.... Regards

answered Nov 27 '14 at 21:32

Villanuevand

86
3

Thanks for help! I think i will study on this "prototype" thing to make sth more clear for myself. – Recomer Nov 28 '14 at 18:53

score 0 · Answer 3 · answered Nov 27 '14 at 18:28

I don't know what you do in this code, but I will do the code like this:

function Square(length){
    this.length = length;

    this.calcSideLength = function() {
        this.sideLength = /* Your code to calculate sideLength */;
    };

    this.calcPerimeter = function() {
        return this.sideLength;
    };

    this.calcArea = function() {
        return this.sideLength * this.sideLength;
    };

    this.calcPerimeter2 = function(n) {
        return n*4;
    };
}

var square = new Square(5);

var p = square.calcPerimeter();
var a = square.calcArea();

var square1 = new Square(5);
square1.calcPerimeter2(/* send a number */);

I Could Not Run My Method -JavaScript

3 Answers3