What's the difference between == and ===?

Model answer

• === is strict equality: true only if both value and type are the same.
• == is loose equality: it converts (coerces) types before comparing.

5 === "5";        // false: number vs string
5 == "5";         // true: "5" is converted to 5
0 == false;       // true
null == undefined; // true
null === undefined; // false

What I use: === almost always, because coercion rules cause surprising bugs and make code harder to reason about. Many teams enforce it with a linter rule (eqeqeq).

Bonus point: the one common exception is value == null, which checks for both null and undefined at once. Some codebases allow it deliberately.

Why interviewers ask: it checks whether you understand types and coercion, not just syntax.