Scope

Scope is where a variable can be seen and used. A variable declared with let/const inside a function (or any { } block) is local — it only exists inside that block, and is invisible outside it.

function setTotal() {
    const total = 100;
    console.log(total); // works: total is visible here
}

setTotal();
console.log(total); // ReferenceError: total is not defined

Common mistakes

• Expecting a variable declared inside a function to be usable outside it. If you need the value outside, return it and store the result in a variable at the outer level.