When should you use a function declaration vs an expression?
Use declarations for top-level helpers you want callable from anywhere. Use const function expressions (often arrows) for everything else, to enforce declare-before-use and avoid hoisting surprises.
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More FAQs in Function Declarations vs Function Expressions in JavaScript
A function declaration is hoisted with its full body, so it can be called before its line. A function expression is assigned to a variable, which is hoisted (undefined with var, TDZ with let/const) but the function body is only assigned at the line.
No. With var, calling it early throws TypeError because the variable is undefined. With let or const, it throws ReferenceError because the variable is in the Temporal Dead Zone.
A function expression with an internal name, like const greet = function sayHi() {}. The internal name is only visible inside the function, useful for recursion and better stack traces. Outside, you use the variable name.
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