closureseasy
What is hoisting?
Answer
Declarations are registered when a scope is created, before any code in it runs. Function declarations are fully available, so you can call them above where they're written. var is registered but initialised to undefined. let and const are registered but unusable until their line executes — that gap is the temporal dead zone, and touching them inside it throws a ReferenceError.
Points an interviewer listens for
- Declarations registered at scope creation, not assignments
- Function declarations are callable before their line
- var reads as undefined; let/const throw in the TDZ
- Function expressions follow their variable's rules
Reported at
Similar questions have been reported by candidates at Deloitte, Neerx Technovation, Photon Technologies, TO THE NEW, Zepto, DotStark Technologies.
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