Question 1

What does console.log(a) print if var a = 5 is below it?

Accepted Answer

undefined. The var declaration is hoisted and initialized to undefined. The assignment a = 5 runs only when the line is reached, so the earlier log sees undefined.

Question 2

What happens when you call a function expression before its assignment?

Accepted Answer

TypeError: x is not a function. The var variable is hoisted with undefined, so calling it as a function fails. Only function declarations are hoisted with their body.

Question 3

Does typeof escape the Temporal Dead Zone?

Accepted Answer

No. typeof on a let or const variable in the TDZ throws ReferenceError. typeof on a var that has not been assigned returns the string 'undefined' without throwing.

Question 4

What happens if two function declarations have the same name?

Accepted Answer

The last one wins. Both are hoisted with their full bodies, and the later declaration overwrites the earlier one in memory. So calls after both declarations always invoke the last one.

What does console.log(a) print if var a = 5 is below it?

More FAQs in Common Hoisting Interview Questions in JavaScript

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