Lesson 1 of 6

const and arrow functions

Modern JavaScript declares with const (or let when the value changes) and writes short functions with arrow syntax: const double = (x) => x * 2;

Without braces, the arrow returns the expression directly — ideal for one-line transformations.

const double = (x) => x * 2;
document.querySelector('#out').textContent = double(21);

🎯 Exercise

Declare an arrow function double (const) that returns its argument times 2, then write double(21) into the #out paragraph.

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