How do you approach shadowing + hoisting questions in a JavaScript interview?
Identify whether the inner declaration is var, let, or const. var is hoisted with undefined (shadows outer immediately). let/const are hoisted but in the TDZ (shadows outer and throws if accessed early). Check for illegal shadowing (let + var in the same scope). Walk through the memory phase first.
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More FAQs in Shadowing and Hoisting Interview Questions in JavaScript
Because the inner var x is hoisted to the top of the function with undefined, shadowing the outer immediately. A read before the assignment line sees undefined, not the outer value. This is the classic shadowing + hoisting trap.
Because the inner let is hoisted (shadowing the outer from the start of the block) and is in the TDZ. It does not fall back to the outer variable. Accessing it before the inner declaration line throws ReferenceError.
3, 3, 3. var is function-scoped, so all callbacks share one i. By the time the callbacks run, the loop has finished and i is 3. Use let to fix this (each iteration gets a fresh binding).
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