#7: null == undefined
Topic: coercion · Difficulty: ★★
console.log(null == undefined);
console.log(null === undefined);
console.log(null == 0);Output
true false false
Why
The spec gives null and undefined a special rule: with loose ==, they equal each other and nothing else (except themselves). === never coerces, and they are different types, so that's false. The interesting trap is null == 0: you might expect null to act like 0 in comparisons since it does in some arithmetic contexts, but the == algorithm never converts null to a number — it only ever compares null/undefined loosely to each other, so null == 0 is false even though Number(null) is 0.
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