Mene map, filter da reduce suke aiki?

Question

Accepted Answer

Sune **immutable** array iterators — suna koma da sabuwar ajiya maimakon canja ainihin, wanda ke haifar da tsafar kuma bayyanar code fiye da manual `for` loops.

```js
const nums = [1, 2, 3, 4];

// map: transform each item → array of the SAME length
nums.map(n => n * 2);            // [2, 4, 6, 8]

// filter: keep items passing a test → SHORTER array
nums.filter(n => n % 2 === 0);  // [2, 4]

// reduce: fold the array into ONE value (accumulator + current)
nums.reduce((sum, n) => sum + n, 0); // 10
//          ^acc  ^item            ^initial value
```

## Yadda reduce ke aiki (wanda mutane ke samun wahala)

Reduce yana taffiya jerin yana dakon "accumulator." Kowane mataki yana koma da sabuwar accumulator:

```js
// step 0: acc=0,  n=1 → 1
// step 1: acc=1,  n=2 → 3
// step 2: acc=3,  n=3 → 6
// step 3: acc=6,  n=4 → 10
```

Ba kaɗai ne don jimlawa — reduce na iya gina abubuwa, tara abubuwa, ko fayyasi:

```js
users.reduce((acc, u) => { acc[u.id] = u; return acc; }, {}); // index by id
```

## Me ya sa aka fi so su

Su **chain** kyau-kyau kuma suna ciyar da canja, wanda ke matukar mahimmanci a cikin state-driven UIs. Yi amfani da `forEach` kawai don sakamako (ba yana koma da komi ba). Ga manyan jerin inda za ka karkata da yawa, gida daya `reduce` ko madaidaita jigon iya zama ma samarwa.