Loops and array methods

What this means

Loops repeat code. Modern JavaScript also uses array methods such as map, filter, and find to process lists clearly.

In beginner terms, this topic answers one practical question: "What should I write, and why does React care about it?" Do not try to memorize the syntax first. First understand the idea, then connect the syntax to that idea.

Why it matters

Lists appear everywhere in software. Looping lets one piece of logic handle many lessons, users, products, or messages.

When you build real React screens, this idea helps you decide where data should live, what the user should see, and what should happen after an interaction. That is why this lesson is part of the main path instead of being an optional detail.

Step by step

1. Notice the UI problem this topic solves. 2. Look at the smallest possible example. 3. Change one value and predict what should appear. 4. Run the example and compare the result with your prediction. 5. Use the practice task before moving on.

Small example

const completed = lessons.filter((lesson) => lesson.done);

Common mistake

Do not create loops that never reach a stopping condition.

Practice task

Filter a list of lesson objects so only completed lessons remain.

Remember this

Use loops and array methods to process lists, not copied code.