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Lesson 21 — Closure factories
Functions that make functions
A factory is a function that builds and returns another function, set up with some value. adder(10) returns a new function that adds 10 to whatever you give it — the 10 is remembered by closure.
const add10 = adder(10);
add10(5); // 15
Why it matters: you can create many specialised helpers (tax calculators, formatters, validators) from one template.
Write multiplier(m) that returns (x) => x * m, then use it to make double and triple.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledgeA quick 3-question quiz on this lesson — instant feedback.
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