Currying na partial application ni nini?

Question

Accepted Answer

**Currying** hubadilisha kazi inayochukua hoja N kuwa mlolongo wa kazi N ambazo kila moja inachukua hoja moja. **Partial application** inabandika hoja *zingine* sasa na kurudisha kazi inayosubiri zingine.

```js
// normal
const add = (a, b, c) => a + b + c;

// curried — one argument at a time
const curriedAdd = a => b => c => a + b + c;
curriedAdd(1)(2)(3); // 6

// partial application — pre-fill some args
const add10 = curriedAdd(10);   // a is fixed at 10
add10(5)(1);                     // 16
```

Kila hatua hutumia **closure** kumbukumbu hoja za awali hadi zote zitolewe.

## Kwa nini ni muhimu: kujenga kazi maalum

```js
const log = level => message => console.log(`[${level}] ${message}`);
const error = log("ERROR");   // reusable, pre-configured logger
const info = log("INFO");
error("disk full");           // [ERROR] disk full
```

Badala ya kurudia kiwango kila mahali, unaumba kazi zilizosanidiwa mara moja. Hii inatozwa sana katika matangazo ya kazi na waendeshaji wa tukio:

```js
const onChange = field => e => setForm(f => ({ ...f, [field]: e.target.value }));
<input onChange={onChange("email")} />  // a handler specialized to "email"
```

## Curry ya jumla / maktaba

Maktaba (Ramda, lodash `curry`) auto-curry kazi yoyote ili uweze kutoa hoja katika vikundi vya kulia.

## Kwa nini inakamatia

Currying huwezesha **muundo safi wa kazi**, callbacks zilizosanidiwa zinazoweza kutumiwa tena, na mtindo bila uhakika.

Ni kawaida katika kodbesi za kazi na mada ya kawaida ya mahojiano kupima uelewa wa closures.