# Symbols in JavaScript

The datatype `symbol` is a primitive datatype along with `null`, `undefined`, `number`, `string` and `boolean`.

Symbols were introduced in the [ECMAScript 2015]() version in 2015.

Unlike like strings, numbers or booleans, symbols have no literals. They have to be created using the `Symbol()` function, the values returned as a result of calling this function is of type `symbol`.

The `Symbol()` function also has some static methods but is incomplete as a constructor so it **cannot** be used with the `new` keyword like this: `new Symbol()`.

## Creating and using a symbol

Every value returned from `Symbol()` is always unique, Hence no two symbols could ever have the same value.

```javascript
Symbol() === Symbol(); // false
```

The values returned from `Symbol()` can never be known as well:

```javascript
const mySymbol = Symbol();
const mySecondSymbol = Symbol('this is a symbol');

console.log(mySymbol); // Symbol()
console.log(mySecondSymbol); // Symbol('this is a symbol')
```

Note: any value passed to the function is not the output value but more like an identifier or description of the symbol.

So symbols are a great way to create properties in an object to avoid clashing.

```javascript
const propertyName = Symbol('unique property');
const myObject = {
	[propertyName]: 'This is a unique property',
 }
 console.log(myObject); // { Symbol(unique property): "This is a unique property" }
 console.log(myObject[propertyName]); // This is a unique property
```

A symbol property is not enumerable so they won't show in [`for...of`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of) and [`for...in`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in) loops. They will not appear in `Object.keys()` and `Object.getOwnPropertyNames()` as well.

There is, however, one method existing on the `Object` constructor: [`Object.getOwnPropertySymbols()`]().

`Object.getOwnPropertySymbols()` returns an array of symbol properties on the object.

### Symbol.for()

The `Symbol.for()` method searches for a specific symbol with the key provided, If the symbol does not exist, it creates a new one in the global symbol registry.

```javascript
const firstSymbol = Symbol.for('mySymbol'); // creates symbol
const secondSymbol = Symbol.for('mySymbol'); // retrieves the symbol

firstSymbol === secondSymbol; // true
```

Since both variables point to the same symbol in memory, when compared, the result evaluates to true.

[You can learn more about symbols here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol).