CODEWITHSUNDEEP
javascript
Alper Ceviz
Alper Ceviz

Reputation: 41

Why returns false without comparison?

console.log([1,2,3] > null); // returns false

// "1,2,3" > null
// NaN > null
// false => Direct returns false ??

The code returns false. Normally NaN > null must be numeric comparison. But result returned false. Why?

Upvotes: 1

Views: 60

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1075567

Following the steps in the Abstract Relational Comparison algorithm:

  • [1,2,3] > null - Step 1 (a,b): Apply ToPrimitive to both sides
  • "1,2,3" > null - Step 4 (d, e): Apply ToNumeric to both sides

Now we have NaN > 0, which is false, because any time NaN is involved in any relational operation, the result is false.

In a comment on the question you asked:

But why returns false without comparison.

> is a comparison. I think you mean "without a branching operation or expression" (like if or the conditional operator, ? :). If so, it's because expressions (including relational expressions) have result values whether or not you use those results for branching. The result of a > expression is true or false. If you use that in an if, that's fine, but you don't have to:

const a = 1 > 2;
console.log(a); // false

Upvotes: 3

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