Question 1

What is the difference between == and === in JavaScript?

Accepted Answer

== compares values after converting their types if needed. === compares both the value and the type, without converting anything. For example, 0 == "" is true, because the empty string converts to 0. 0 === "" is false, because the types differ. Use === by default, because it avoids surprising conversions.

Question 2

What is a closure in JavaScript?

Accepted Answer

A closure is a function that keeps access to the variables of the scope where it was created, even after that outer function has returned. It is the mechanism behind private state. For example, a counter function can hold its count inside a closure, so the count is not reachable from outside but still updates on every call. Closures are common in event handlers and callbacks.