What Is Symbol Data Type in JavaScript?


Angela Bailey

JavaScript is a versatile programming language that offers a wide range of data types to work with. One such data type is the symbol data type. In this article, we will explore what the symbol data type is and how it can be used in JavaScript.

What is a Symbol?

A symbol in JavaScript is a unique and immutable primitive value that can be used as the key for an object property. Unlike other primitive data types such as strings or numbers, symbols cannot be changed once they are created. Each symbol value created using the Symbol() function is unique, even if they have the same description.

Creating Symbols

To create a symbol, you can use the Symbol() function. Let’s take a look at an example:

const mySymbol = Symbol();

In this example, we have created a new symbol and assigned it to the variable `mySymbol`. It’s important to note that calling `Symbol()` without any arguments will create a unique symbol each time it’s called.

Symbols with Descriptions

Symbols can also be created with descriptions, which can be useful for debugging purposes or providing additional information about the symbol. To create a symbol with a description, you can pass a string as an argument to the Symbol() function:

const mySymbol = Symbol(‘This is my symbol’);

In this example, we have created a new symbol with the description “This is my symbol”. The description does not affect the uniqueness of the symbol; two symbols with different descriptions are still considered different.

Using Symbols as Object Properties

One of the main use cases for symbols in JavaScript is as keys for object properties. Symbols are unique and cannot collide with other properties, making them ideal for creating “hidden” or “private” properties.

Let’s see an example:

const mySymbol = Symbol(‘myKey’);
const myObject = {};

myObject[mySymbol] = ‘Hello, symbol!’;

In this example, we have created a symbol `mySymbol` with the description “myKey”. We then assign the value `’Hello, symbol!

‘` to `myObject[mySymbol]`. The use of symbols as keys ensures that this property is not accidentally overwritten or accessed by other parts of the code.

Iterating Over Object Properties

Symbols are not enumerable in for..in loops or by using the Object.keys() method. However, they can be accessed using Object.getOwnPropertySymbols() method. This makes symbols useful for creating “hidden” properties that are not intended to be iterated over.

Consider the following example:

const mySymbol = Symbol(‘myKey’);
const myObject = {
[mySymbol]: ‘Hello, symbol!’

// Output: [Symbol(myKey)]

In this example, we have created an object `myObject` with a property `[mySymbol]`. When we log `Object.getOwnPropertySymbols(myObject)`, it returns an array containing the symbol `Symbol(myKey)`.


The symbol data type in JavaScript provides a way to create unique and immutable values that can be used as keys for object properties. Symbols are useful for creating private or hidden properties and cannot be accidentally overwritten. Although symbols cannot be changed once created, they are still garbage collected when there are no references to them anymore.

In summary, symbols add another level of flexibility and control to JavaScript programming, allowing developers to create more robust and secure code. Incorporating symbols into your projects can help improve code organization and reduce the risk of naming collisions.

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