Why Empty Arrays Equal Zero But Not Each Other, Double Equals Confusion and Loose Equality in JavaScript: Why These Arrays Don’t Behave as Expected.

Our code :-

console.log([] == 0);
console.log([0] == [0]);

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🔹 Line 1: [] == 0

Step-by-step:

1. Operands:
• Left: [] → an empty array (object).
• Right: 0 → a number.
2. Loose equality == allows type coercion, so JavaScript tries to make the types match.
3. [] is an object. When comparing an object to a primitive, JavaScript first converts the object to a primitive using ToPrimitive.
4. So:
• [] → "" (an empty string)
• (because .toString() on an empty array returns "")

5. Now the expression becomes:

• "" == 0

6. Next, JavaScript converts both sides to numbers:

• "" → 0
• 0 stays 0

7. Now it’s:

• 0 == 0 // true

✅ Result: true

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🔹 Line 2: [0] == [0]

Step-by-step:

1. Both sides are arrays, each containing a single element: 0.
2. Arrays are objects in JavaScript, and objects are compared by reference, not by value.

3. [0] == [0] is comparing:

• Two different array instances (in memory), even though they contain the same value.

4. Since they’re not the same object in memory:

• false

✅ Result: false

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✔ Final Answer:

A) true false

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