Lesson 13 — Controlled input

You decide what gets stored

Because a controlled input shows whatever is in state, your onChange handler can change the value before saving it: trim it, uppercase it, or cut it to a maximum length. The input then shows your version, not the raw keystrokes.

function onChange(e) {
  setCode(e.target.value.toUpperCase()); // always shows capitals
}

Why it matters: this is how apps enforce limits like "max 280 characters" or "digits only" while the user types.