Menene Symbols kuma ana amfani da su a waje?

Question

Accepted Answer

**Symbol** shine nau'i na musamman, wanda ba za a iya canjewa ba. Kowane `Symbol()` da ka aiki **jami'an daidai** — har ma da biyu masu cikakken bayanai daidai ba su daidai ba. Aiki na musamman shine zama **maɓuɓɓuki na juyawa na abubuwa** maida ba ta tabbata.

```js
const id = Symbol("id");
const id2 = Symbol("id");
id === id2;        // false — always unique

const user = { [id]: 123, name: "Ann" };
user[id];          // 123
```

## Me yasa aljihu na musamman suke da amfani

Aikin Symbol-keyed ba ya kasua da juyawa na jeri da **boye** ne daga tallafi na yau yau — cikakke don daura ta bayani ba tare da gida abubuwa ba:

```js
Object.keys(user);          // ["name"]  — symbol key is skipped
for (const k in user) {}    // skips the symbol
JSON.stringify(user);       // {"name":"Ann"} — symbol not serialized
Object.getOwnPropertySymbols(user); // [Symbol(id)] — only way to list them
```

Don haka karatu zai iya adana bayani na ciki a abubuwa ta hanyar Symbol ba tare da haɗi da abubuwan ku ba ko nunawa a cikin kewayon ku ba.

## Alamomi sanannun jiya suna bada alamomi halaka tumanin harshe

Amfanin mahimmi - `Symbol.iterator` saya abubuwa wakan iya:

```js
const range = {
  [Symbol.iterator]() {
    let i = 1;
    return { next: () => (i <= 3 ? { value: i++, done: false } : { done: true }) };
  },
};
[...range]; // [1, 2, 3]
```

Jiya: `Symbol.asyncIterator`, `Symbol.toPrimitive` (sauye na sirri), `Symbol.hasInstance`.

## Jerin duniya

```js
Symbol.for("key"); // shared symbol across the whole app (and across realms)
```

## Me yasa hakan mahimmi

Allamomi suna ba da damar alamomi bayani ba tare da haɗi da jeri da ba su ba wa abubuwan yada jiya da jiya (juyawa, sauye) — yadda aka gida jiya da jiya zasu sami abubuwan halaka.