JavaScript: Why is the output false?

Question

// These are true

console.log(window === this)
console.log(window === self)
console.log(this === self)

console.log(window === this === self) // Why is this false?

window is equal to this,
window is equal to self, and
this is equal to self

So, why is window === self === this false in JavaScript

because `a === b === c` is equivalent to `(a === b) === c`, thus `true === c` which is obviously wrong if `c` is not boolean — derpirscher, Nov 21 '21 at 16:12

score 1 · Answer 1 · answered Nov 21 '21 at 16:12

1

Because true is not equal to this.

This expression:

window === self === this

Is equivalent to:

true === this

Which is false, because this is not a boolean.

answered Nov 21 '21 at 16:12

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score 0 · Answer 2 · answered Nov 21 '21 at 16:14

Because you can't chain equality operators in such a way in javascript. window === this === self is actually the same as: (window === this) === self where the parentheses is evaluated first. In other words window === this === self equals true === self which evaluates to false.

JavaScript: Why is the output false?

2 Answers2