JavaScript: Number Object

Number is the value of the property key "Number" of the Global Object .

console.log( window.Number === Number ); // true

Type

Type of Number is a function.

console.log( typeof Number === "function" ); // true

Parent

Parent of Number is Function.prototype. [see Prototype and Inheritance]

console.log( Reflect.getPrototypeOf ( Number ) === Function.prototype ); // true

Purpose

Purpose of Number is:

• Implicitly called by JavaScript to work on number type values. Example: let x = 3;x.toString(). JS first convert the number primitive value to a number object, so that it has method toString.
• Holds useful value properties such as Number.MAX_VALUE and function properties such as parseInt.
• Has the property key "prototype" that is the parent object of number object. It has properties such as toFixed.

Number Primitive and Number Object

Literal numbers such as 3 are Primitive Value. That is, the type of a number such as 3, is number, not object.

Number primitive include special literal expression NaN and Infinity .

You can convert a primitive number type to a number object type by new Number(num).

Number Constructor

Number Constructor

Properties

• prototype
• parseInt
• parseFloat
• isFinite
• isInteger
• isNaN
• isSafeInteger

Number.NaN

Value is NaN.

console.log( Number.isNaN( Number.NaN ) ); // true

Number.NEGATIVE_INFINITY

Value is -Infinity.

console.log( Number.NEGATIVE_INFINITY === -Infinity ); // true

Number.POSITIVE_INFINITY

Value is +Infinity.

console.log( Number.POSITIVE_INFINITY === Infinity ); // true

Number.MIN_SAFE_INTEGER

Value is -9007199254740991 (same as -(2^53-1)).

It's the smallest integer n such that n and n - 1 are both exactly representable as a Number value.

console.log(Number.MIN_SAFE_INTEGER === -9007199254740991); // true
console.log(-9007199254740991 === -(2 ** 53 - 1)); // true

Number.MAX_SAFE_INTEGER

Value is 9007199254740991. Same as (2^53 - 1).

It's the largest integer n such that n and n + 1 are both exactly representable as a Number value.

console.log( Number.MAX_SAFE_INTEGER === 9007199254740991 ); // true

Number.EPSILON

Value is the difference between 1 and the smallest value greater than 1 that is representable as a Number value, which is approximately 2.2204460492503130808472633361816 x 10^(-16).

console.log( Number.EPSILON === 2.220446049250313e-16 ); // true

Number.MIN_VALUE

The value is the smallest positive value of the Number type, which is approximately 5 × 10^(-324).

In the IEEE 754-2008 double precision binary representation, the smallest possible value is a denormalized number. If an implementation does not support denormalized values, the value of Number.MIN_VALUE must be the smallest non-zero positive value that can actually be represented by the implementation.

console.log( Number.MIN_VALUE === 5e-324 ); // true

Number.MAX_VALUE

The value is the largest positive finite value of the Number type, which is approximately 1.7976931348623157 × 10^308.

console.log( Number.MAX_VALUE === 1.7976931348623157e+308 ); // true