Control flow and functions · 15 MIN

Scope and closures

Global, function and block scope determine where bindings are visible. A closure occurs when a function retains access to variables from its surrounding lexical scope. Closures are useful for private state and callbacks.

Try it yourself

Change the example, run it, and explain the result in your own words. Then create one variation of your own.

Key idea

Use the example as a starting point, not something to memorize. Practise, inspect the result and make small improvements.

Code example

function makeCounter() {
  let count = 0;
  return () => ++count;
}
const next = makeCounter();
console.log(next(), next());

Practise this lesson