TheSymbol() function returns primitive values of type Symbol.

Try it

const symbol1 = Symbol();const symbol2 = Symbol(42);const symbol3 = Symbol("foo");console.log(typeof symbol1);// Expected output: "symbol"console.log(symbol2 === 42);// Expected output: falseconsole.log(symbol3.toString());// Expected output: "Symbol(foo)"console.log(Symbol("foo") === Symbol("foo"));// Expected output: false

Syntax

Symbol()Symbol(description)

Parameters

descriptionOptional

A string. A description of the symbol which can be used for debugging but not toaccess the symbol itself.

Examples

Creating symbols

To create a new primitive symbol, you writeSymbol() with an optionalstring as its description:

const sym1 = Symbol();const sym2 = Symbol("foo");const sym3 = Symbol("foo");

The above code creates three new symbols. Note thatSymbol("foo") does notcoerce the string"foo" into a symbol. It creates a new symbol each time:

Symbol("foo") === Symbol("foo"); // false

new Symbol()

The following syntax with thenew operator will throw aTypeError:

const sym = new Symbol(); // TypeError

This prevents authors from creating an explicitSymbol wrapper objectinstead of a new symbol value and might be surprising as creating explicit wrapperobjects around primitive data types is generally possible (for example,new Boolean,new String andnew Number).

If you really want to create aSymbol wrapper object, you can use theObject() function:

const sym = Symbol("foo");const symObj = Object(sym);typeof sym; // "symbol"typeof symObj; // "object"

Specifications

Browser compatibility

See also

• Polyfill ofSymbol incore-js