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Boolean Operators

The operators that return a Boolean value are:
>: greater than
>=: greater than or equals
<: less than
<=: less than or equals
==: equals in evaluated value
===: equals in value and type
in: is a property of
instanceof: is an object of


console.log(3 < 3);
console.log(3 <= 3);
console.log(3 == 3);
console.log(3 === 3);

console.log(3 == new Number(3));
console.log(3 === new Number(3));
console.log(typeof 3);
console.log(typeof new Number(3));
console.log(new Number(3) == new Number(3));
console.log(new Number(3) === new Number(3));

false true true true true false number object false false

function F() {
  this.x = 100;
}

class C extends F {}

var o = new C;
console.log(o instanceof C);
console.log(o instanceof F);
console.log('x' in o);

true true true

To assign default values, the or operator(||) or the nullish coaslescing operator(??) can be used.


const
  nullValue = null,
  numberValue = 300,
  zeroValue = 0,
  emptyValue = '',
  falseValue = false;

console.log(nullValue || 'DEFAULT');
console.log(numberValue || 'DEFAULT');
console.log(zeroValue || 'DEFAULT');
console.log(emptyValue || 'DEFAULT');
console.log(falseValue || 'DEFAULT');

console.log("........................");

console.log(nullValue ?? 'DEFAULT');
console.log(numberValue ?? 'DEFAULT');
console.log(zeroValue ?? 'DEFAULT');
console.log(emptyValue ?? 'DEFAULT');
console.log(falseValue ?? 'DEFAULT');

DEFAULT 300 DEFAULT DEFAULT DEFAULT ........................ DEFAULT 300 0 '' false