Symbol() constructor
{{JSRef}}
The Symbol() function returns primitive values of type Symbol.
{{InteractiveExample("JavaScript Demo: Symbol - Constructor", "taller")}}
const symbol1 = Symbol();
const symbol2 = Symbol(42);
const symbol3 = Symbol("foo");
console.log(typeof symbol1);
// Expected output: "symbol"
console.log(symbol2 === 42);
// Expected output: false
console.log(symbol3.toString());
// Expected output: "Symbol(foo)"
console.log(Symbol("foo") === Symbol("foo"));
// Expected output: false
Syntax
Symbol()
Symbol(description)
Note:
Symbol()can only be called withoutnew. Attempting to construct it withnewthrows a{{jsxref("TypeError")}}.
Parameters
description{{optional_inline}}- : A string. A description of the symbol which can be used for debugging but not to access the symbol itself.
Examples
Creating symbols
To create a new primitive symbol, you write Symbol() with an optional
string as its description:
const sym1 = Symbol();
const sym2 = Symbol("foo");
const sym3 = Symbol("foo");
The above code creates three new symbols. Note that Symbol("foo") does not
coerce the string "foo" into a symbol. It creates a new symbol each time:
Symbol("foo") === Symbol("foo"); // false
new Symbol()
The following syntax with the {{jsxref("Operators/new", "new")}} operator will throw a
{{jsxref("TypeError")}} :
const sym = new Symbol(); // TypeError
This prevents authors from creating an explicit Symbol wrapper object
instead of a new symbol value and might be surprising as creating explicit wrapper
objects around primitive data types is generally possible (for example,
new Boolean, new String and new Number).
If you really want to create a Symbol wrapper object, you can use the
Object() function:
const sym = Symbol("foo");
const symObj = Object(sym);
typeof sym; // "symbol"
typeof symObj; // "object"
Specifications
{{Specifications}}
Browser compatibility
{{Compat}}