Learn ECMAScript - Second Edition

Symbols – primitive data type

Symbols are a primitive type that was first introduced in ES6. A symbol is a unique and immutable value. Here is an example that shows how to create a symbol:

const s = Symbol();

Symbols don't have a literal form; therefore, we need to use the Symbol() function to create a symbol. The Symbol() function returns a unique symbol every time it is called.

The Symbol() function takes an optional string parameter that represents the description of the symbol. A description of a symbol can be used for debugging, but not to access the symbol itself. Two symbols with the same description are not equal at all. Here is an example to demonstrate this:

let s1 = Symbol("My Symbol");let s2 = Symbol("My Symbol");console.log(s1 ...