In JavaScript, what is the scope of a function declared within the condition of an if statement?

Question

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Answer 1

f is not in scope because it is an inline named function expression. It is not a function declration. The differences are subtle but important -

// declaration
function f () { ... }

// named function expression
const foo = function f () { ... }

// named arrow expression
const f = () => { ... }

// unnamed arrow expression
() => { ... }

The semantics of if help us understand -

if (<expression>) {
  <consequent>
} else {
  <alternative>
}

As you can see, the conditional supplied to an if statement must be an expression. You cannot declare a variable in an expression. This includes function declarations.