primitive. However, the typeof operator does not return boolean for the

object wrapper, it returns object. Because all objects evaluate as true,

a method such as .valueOf(), or .toString(), must be used to retrieve

the wrapped value. For explicit coercion to the Boolean type, Mozilla

recommends that the Boolean() function (without new) be used in

preference to the Boolean object.

const b = new Boolean(false); // Object false {}

const t = Boolean(b); // Boolean true

const f = Boolean(b.valueOf()); // Boolean false

let n = new Boolean(b); // Not recommended

n = new Boolean(b.valueOf()); // Preferred

|| !t) {

console.log("Never this");

"false") {

console.log("Always this");

}

Symbols are a feature introduced in ES6. Each symbol is guaranteed to be

a unique value, and they can be used for encapsulation.cite-ref-15[15]

Example:

let x = Symbol(1);

const y = Symbol(1);

x === y; // => false

const symbolObject = {};

const normalObject = {};

// since x and y are unique,

// they can be used as unique keys in an object

symbolObject[x] = 1;

symbolObject[y] = 2;

symbolObject[x]; // => 1

symbolObject[y]; // => 2

// as compared to normal numeric keys

normalObject[1] = 1;

normalObject[1] = 2; // overrides the value of 1

normalObject[1]; // => 2

// changing the value of x does not change the key stored in the object