What Is a Symbol Data Type?


Larry Thompson

What Is a Symbol Data Type?

A symbol data type is a unique feature in certain programming languages that allows developers to define and work with symbols. Symbols are immutable and unique identifiers that can be used as keys in dictionaries or as labels for variables, functions, or other data structures.

Why Use Symbols?

Symbols are Unique:

Symbols are guaranteed to be unique within the context of a program. This uniqueness makes symbols useful when you want to create keys for dictionaries or need globally unique identifiers.

Symbols are Immutable:

Unlike strings, symbols are immutable, meaning they cannot be modified once they are created. This immutability makes them ideal for scenarios where you want to ensure the integrity of an identifier.

How to Create Symbols

In most programming languages that support symbol data types, symbols can be created using a specific syntax. Here’s an example of how to create a symbol:

const mySymbol = Symbol('mySymbol');

In this example, we use the Symbol() function and pass a string as its parameter. The string is optional and can be used for debugging or providing additional information about the symbol.

Working with Symbols

Using Symbols as Dictionary Keys:

Symbols can be used as keys in dictionaries or objects. Unlike strings, symbols do not clash with other property names and ensure that each key is unique.

const myObject = {};

const mySymbol = Symbol('mySymbol');
myObject[mySymbol] = 'Some value';

console.log(myObject[mySymbol]); // Output: Some value

Using Symbols to Define Constants:

Symbols can be used as constant values to define unique identifiers. This helps prevent accidental modification of important variables or properties.

const RED = Symbol('red');
const BLUE = Symbol('blue');
const GREEN = Symbol('green');

let color = GREEN;

if (color === GREEN) {
  console.log('The color is green.');


Symbols are powerful tools in programming languages that provide unique and immutable identifiers. They are particularly useful when you need to create keys for dictionaries, define constants, or ensure the integrity of an identifier. By incorporating symbols into your code, you can improve the organization and readability of your programs.

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