How is the value of `this` determined?

Answer

For a normal function it's decided by how it's called, not where it's written: called as obj.method() it's obj; called bare it's undefined in strict mode; with new it's the new instance; and call/apply/bind set it explicitly. Arrow functions have no own this — they use the enclosing scope's, which is exactly why they're the safe choice for callbacks inside a method.

Points an interviewer listens for

• Determined at call time for normal functions
• Method call → the object; bare call → undefined in strict mode
• new → the instance; call/apply/bind → explicit
• Arrows inherit this from the enclosing scope

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