"use strict";

//------------------------------------------------------------------------------

// Symbol Type

// Unique and immutable data type to be used as an identifier for object

// properties. Symbol can have an optional description, but for debugging

// purposes only.

// http://es6-features.org/#SymbolType

//------------------------------------------------------------------------------

Symbol("foo") !== Symbol("foo")

const foo = Symbol()

const bar = Symbol()

typeof foo === "symbol"

typeof bar === "symbol"

let obj = {}

obj[foo] = "foo"

obj[bar] = "bar"

JSON.stringify(obj) // {}

Object.keys(obj) // []

Object.getOwnPropertyNames(obj) // []

Object.getOwnPropertySymbols(obj) // [ foo, bar ]

//------------------------------------------------------------------------------

// Global Symbols

// Global symbols, indexed through unique keys.

// http://es6-features.org/#GlobalSymbols

//------------------------------------------------------------------------------

Symbol.for("app.foo") === Symbol.for("app.foo")

const foo = Symbol.for("app.foo")

const bar = Symbol.for("app.bar")

Symbol.keyFor(foo) === "app.foo"

Symbol.keyFor(bar) === "app.bar"

typeof foo === "symbol"

typeof bar === "symbol"

let obj = {}

obj[foo] = "foo"

obj[bar] = "bar"

JSON.stringify(obj) // {}

Object.keys(obj) // []

Object.getOwnPropertyNames(obj) // []

Object.getOwnPropertySymbols(obj) // [ foo, bar ]