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Closures
hardComplete guide with examples and interview questions · 35 min
Definition
Say it out loud in an interview — clear, simple, no textbook wording.
A closure forms when a function is defined inside another function and remembers variables from the outer scope — even after the outer function has returned.
Closures are the mechanism behind encapsulation in JavaScript without classes.
Quick Stats
35
Minutes
hard
Difficulty
4
Interview Q's
Key takeaways
- •A closure is a function plus its lexical environment
- •Inner functions retain access to outer variables after the outer function returns
- •Closures power private state, callbacks, and partial application
- •Classic loop-with-var interview trap tests closure understanding
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