How to Learn the JavaScript Array Methods
Arrays are everywhere in JavaScript, and a couple of dozen built-in methods do most of the work — adding, removing, transforming and searching. Learn map, filter and reduce especially and your code gets far cleaner. This deck teaches the essentials.
There are 14 cards in the deck below. You can read through them, practise them right here with the flip-card player, and then save the deck to study properly with spaced repetition — the method that makes them stick for months, not minutes.
Why the JavaScript array methods is hard to memorize (and the fix)
The confusing pairs are push/pop vs shift/unshift (which end?) and slice vs splice (does it change the original?). Learning each precisely avoids subtle bugs.
The fix is active recall plus spaced repetition. Instead of re-reading the list (which feels productive but barely works), you test yourself — pull each answer out of memory — and you review each card on a schedule that stretches over time. Every time you successfully recall a fact, the memory gets stronger and the next review is pushed further out. That's how you go from "I saw it once" to "I just know it."
The fastest way to learn the JavaScript array methods
- Break it into small batches. Learn the add/remove methods first (push, pop, shift, unshift), then the transformers (map, filter, reduce), then the searchers (find, includes, indexOf).
- Test, don't re-read. Look at the question, say the answer out loud before flipping the card. The little struggle to recall is what builds the memory — a smooth re-read does almost nothing.
- Review on a schedule. Spaced repetition shows you each card right before you'd forget it. Get one right and it comes back in a few days, then a week, then a month. Miss one and it comes back sooner.
- Keep sessions short and daily. Five to ten minutes a day beats a two-hour cram every time. Consistency is the whole game.
One fact per card. map, filter and reduce return NEW arrays — they do not change the original. push, pop and splice DO change it.
The full deck: the JavaScript Array Methods
Here's every card in the set. Practise them above, or save the deck and let spaced repetition schedule your reviews automatically.
| Method | What it does |
|---|---|
| What does .push() do? | Adds one or more items to the END of an array |
| What does .pop() do? | Removes the LAST item and returns it |
| What does .shift() do? | Removes the FIRST item and returns it |
| What does .unshift() do? | Adds one or more items to the START |
| What does .map() do? | Returns a new array with each item transformed |
| What does .filter() do? | Returns a new array of items that pass a test |
| What does .reduce() do? | Reduces an array to a single value (e.g. a sum) |
| What does .forEach() do? | Runs a function once for each item (returns nothing) |
| What does .find() do? | Returns the first item that matches a test |
| What does .includes() do? | Returns true if the array contains a value |
| What does .slice() do? | Returns a copy of part of the array (does not change it) |
| What does .splice() do? | Adds/removes items in place (changes the array) |
| What does .join() do? | Joins all items into a single string |
| Which methods return a new array? | map, filter, slice (they do not mutate the original) |
Save this deck and actually remember it
Create a free account, keep this 14-card deck, and we'll schedule every review at the perfect moment. First deck free forever — no credit card.
Study this deck free →FAQ: learning the JavaScript array methods
How long does it take to learn the JavaScript array methods?
Most people can lock in the JavaScript array methods within one to three weeks of short daily sessions. With spaced repetition doing 10–14 cards a day, you'll recognise them within days and recall them reliably within a couple of weeks.
What's the best way to memorize the JavaScript array methods?
Active recall plus spaced repetition. Test yourself instead of re-reading, and review on a schedule that spaces the cards out over time. Flashcards are built for exactly this — which is why the deck above is the fastest path.
Is this deck free?
Yes. You can practise all 14 cards on this page for free with no account. Sign up (also free) to save the deck and let spaced repetition schedule your reviews so it sticks long-term.