function square(n) { return n * n; }
const result = square(4); // 16
// Anywhere you see square(4), you can replace it with 16Referential transparency means you can replace a call with its return value everywhere.
A hallmark of pure functions is referential transparency: you can replace a function call with its return value without changing program behavior.
Challenge: Implement a pure multiply function and verify that calling it multiple times with the same inputs always produces identical results.