Symbols

https://hacks.mozilla.org/2015/06/es6-in-depth-symbols/

<script>
    function w(wcon) {
        console.log(wcon)
    }
    w(Symbol)
    w(Symbol())
    w(Symbol("foo") !== Symbol("foo"))
    //true
    const foo = Symbol()
    w(foo)
    const bar = Symbol()
    typeof foo === "symbol"
    w(typeof foo === "symbol")
    //true
    var sym = Symbol("<3");
    // "your symbol is " + sym
    // Uncaught TypeError: Cannot convert a Symbol value to a string
    w(String(sym))
    //Symbol(<3)
    w(sym.toString())
    //Symbol(<3)
    w("your symbol is " + String(sym))
    //your symbol is Symbol(<3)
    w("your symbol is " + sym.toString())
    //your symbol is Symbol(<3)
</script>