Javascript OOP Method return " is not a function"

Question

As new on JS developpment, I've started the OOP which from my point of view is the more dificult but also the most intersting part of JS.

There is my code :

var calc = function(num1, num2){
  this.num1 = num1;
  this.num2 = num2;
  this.addNum2 = function(number){
    this.num2 = number;
  }
}

And now, I'm trying to use the function addNum2to set the num2 with

calc.addNum2(24)

I got this return:

VM495:1 Uncaught TypeError: calc.addNum2 is not a function

I'm just here to understand how it works so any help would be precious. Thank you all!

calc is a construtor which constructs an object which has the method addNum2. You use it as new calc(a, b) first… — deceze
– deceze ♦, Commented Nov 3, 2019 at 10:40

Code Maniac · Accepted Answer · 2019-11-03 11:17:38Z

3

You need to invoke function with new operator

function calc(num1, num2) {
  this.num1 = num1;
  this.num2 = num2;
  this.addNum2 = function(number) {
    this.num2 = number;
  }
}

let newCalc = new calc()
newCalc.addNum2(2)
console.log(newCalc.num2)

Or you need to return this from function

function calc(num1, num2) {
  this.num1 = num1;
  this.num2 = num2;
  this.addNum2 = function(number) {
    this.num2 = number;
  }
  return this
}

let newCalc = calc()
newCalc.addNum2(2)
console.log(newCalc.num2)

i would like to do let's say : newCalc.addNum2(4).mutiply(5);

function calc(num1, num2) {
  this.num1 = num1;
  this.num2 = num2;
  this.addNum2 = function(number) {
    this.num2 = number;
    return this
  }
  this.multiply = function(number){
    this.num2 = this.num2 * number
    return this
  }
  return this
}

let newCalc = calc()
newCalc.addNum2(2).multiply(3)
console.log(newCalc.num2)

edited Nov 3, 2019 at 11:17

answered Nov 3, 2019 at 10:40

Code Maniac

37.9k5 gold badges44 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

deceze Over a year ago

You're missing the arguments to calc…

Code Maniac Over a year ago

@deceze i left intentionally so i can show the function is actually changing the value. but yes i could have used different values too

Kevkeev13 Over a year ago

Thank you so much for your answer! My main concern was, is it possible to call "calc" without giving him parameter, and set it later with "addNum" and I can see it's possible! Thanks so much!

Kevkeev13 Over a year ago

@CodeManiac Just last question, if for example i would like to do let's say : newCalc.addNum2(4).mutiply(5); In that case, how shall i structure it?

Code Maniac Over a year ago

@Kevkeev13 You need to return this from functions so you can chain methods. so you need to return this from both addNum2 and multiply function. see the last snippet you can do something like this

Collectives™ on Stack Overflow

Javascript OOP Method return " is not a function"

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related