Access and change array values inside class javascript

Question

I have this simple code:

var num = [12,13]
class Test {
  constructor(num){
    this.num = num
  }

  change() {
  this.num[1] = 5
  }

}

test = new Test(5)
test.change()
alert(test.num[0] + ' x ' + num)

I am trying to change the value of this.num through the change method. However, I get the following error:

Uncaught TypeError: Cannot create property '1' on number '5'

Can someone please explain what I am doing wrong here? Here's a fiddle, if it helps. Thank you

As the error is trying to tell you, a number is not an array. — SLaks
– SLaks, Commented Mar 17, 2019 at 16:17
you pass 5 to the constructor of Test, a number is not iterable — Shane
– Shane, Commented Mar 17, 2019 at 16:17

Maheer Ali · Accepted Answer · 2019-03-17 16:18:29Z

1

You are passing num = 5 to constructor. And this.num will be 5. num inside constructor is not refering to the num in global scope. Instead it creates a private variable num which is passed as 5

You should pass num to contructor()

var num = [12,13]
class Test {
  constructor(num){
    this.num = num
  }

  change() {
    this.num[1] = 5
  }

}

test = new Test(num)
test.change()
alert(test.num[0] + ' x ' + num)

answered Mar 17, 2019 at 16:18

Maheer Ali

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