CODEWITHSUNDEEP
javascript
Hydsoled
Hydsoled

Reputation: 59

Why this code returns a NaN?

function m(age) {
  this.d = second;
}

function second() {
  var k = 65 - this.age;
  return k;
}

var asd = new m(20);
document.write(asd.d());

Why this code doesn't print out 45? I think I did almost same as this YouTube video, but mine doesn't work.

Please also explain why I don't need '()' after second here?:

function m(age) {
    this.d = second;
}

Upvotes: 1

Views: 78

Answers (1)

CertainPerformance
CertainPerformance

Reputation: 370679

You need to assign the age parameter passed to the constructor to this.age so that referencing this.age refers to it properly later. Otherwise, as in your code, the age parameter is passed but never used and subsequently discarded:

function m(age) {
  this.age = age;
  this.d = second;
}

function second() {
  var k = 65 - this.age;
  return k;
}

var asd = new m(20);
document.write(asd.d());

You might consider using a linter - the no-unused-vars rule would have alerted you to the problem.

Upvotes: 3

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