Why [] == ![] is True in JavaScript – The Weirdest Comparison Explained! Here's Why JavaScript Says It's True and JavaScript Logic Uncovered

Our code :-

console.log([] == ![]);

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Step 1: Evaluate Right-Hand Side – ![]

• ![] means: logical NOT of an array

But wait — is an array [] truthy or falsy?

In JavaScript, all objects are truthy, including empty arrays.

So:

![] → !truthy → false

👉 So now the expression becomes:

[] == false

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Step 2: Coerce Both Sides – [] == false

Now we’re comparing:

• [] → object
• false → boolean

Rule:

When comparing an object with a primitive using ==, JavaScript:

• Tries to convert the object to a primitive (usually a string or number)

So:

[] → ""   // empty array becomes empty string via `.toString()`

Now it becomes:

"" == false

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Step 3: Compare "" == false

Now both sides are primitives, but different types:

• "" is a string
• false is a boolean

Again, JavaScript tries to coerce them to numbers:

"" → 0
false → 0

So it becomes:

0 == 0 → true

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✔ Final Answer:

A) true

This question appeared in the TCS 2nd round of interview, testing the candidate’s knowledge of comparisons operator between arrays with inversion operator  in JavaScript.