Lesson 23 — Memoize (expert)

Never compute the same thing twice

Memoization wraps a function with a cache: the first call with an input computes and stores the result; later calls with the same input return the stored result instantly. A Map is a good cache — has, get and set do exactly what they say. It only works for pure functions (same input → always the same output, no side effects).

Why it matters: expensive calculations (prices, layouts, recursive math) become instant on repeat.