TypeScript · Type Alias

symbol

symbol is a primitive type for immutable, unique values created with Symbol(). It can be used for object-property keys, while unique symbol preserves the identity of a specific symbol.

Since: ECMAScript 2015

How it works

The symbol type represents primitive values created with Symbol(). Symbols are immutable and unique, so they can safely serve as object-property keys; use unique symbol when the type system must preserve one specific symbol identity.

Syntax

let value: symbol = Symbol(description);

Key points

symbol is a JavaScript primitive type alongside types such as number and string.
Create symbol values by calling Symbol(), optionally passing a description.
Each symbol is immutable and uniquely identifiable.
Symbols are suitable for computed object-property keys.
Computed symbol properties work in object and class declarations.
Use unique symbol for types that represent a particular symbol literal.

Common mistakes

Two symbols created with the same description are still different values; do not compare them as equal.
A symbol key is accessed with bracket notation, not dot notation.
The broader symbol type does not retain the identity of one particular symbol; use unique symbol when that distinction matters.

Example: Using symbol as an object key

const id: symbol = Symbol("id");
const record = { [id]: "value" };
console.log(record[id]);

This creates a symbol value, uses it as a computed property key, and reads the corresponding property.

When to use it

Private-like property keys

Create collision-resistant keys for object properties.

Computed object members

Define computed properties whose keys are symbols.

General symbol annotations

Represent symbol values without preserving one exact identity.

Unique symbol identities

Model a particular exported symbol constant.

unique symbol
Symbol
computed property declarations

Source: Symbols. Checked 2026-10-15.