TS2448

Block-scoped variable 'add' used before its declaration.

Broken Code ❌

Function expressions cannot be hoisted (used before they are declared):

add(1, 2);
 
const add = (a: number, b: number): number => {
  return a + b;
};

Fixed Code ✔️

Turn your function expression into a function declaration (which can be hoisted):

add(1, 2);
 
function add(a: number, b: number): number {
  return a + b;
}