Number

The Number JavaScript object is a wrapper object allowing you to work with numerical values. A Number object is created using the Number() constructor.

Syntax

new Number(value);

Parameters

value

The numeric value of the object being created.

Description

The primary uses of the Number object are:

• If the argument cannot be converted into a number, it returns NaN.
• In a non-constructor context (i.e., without the new operator), Number can be used to perform a type conversion.

Properties

Number.EPSILON

The smallest interval between two representable numbers.

Number.MAX_SAFE_INTEGER

The maximum safe integer in JavaScript (253 - 1).

Number.MAX_VALUE

The largest positive representable number.

Number.MIN_SAFE_INTEGER

The minimum safe integer in JavaScript (-(253 - 1)).

Number.MIN_VALUE

The smallest positive representable number - that is, the positive number closest to zero (without actually being zero).

Number.NaN

Special "not a number" value.

Number.NEGATIVE_INFINITY

Special value representing negative infinity; returned on overflow.

Number.POSITIVE_INFINITY

Special value representing infinity; returned on overflow.

Number.prototype

Allows the addition of properties to a Number object.

Methods

Number.isNaN()

Determine whether the passed value is NaN.

Number.isFinite()

Determine whether the passed value is a finite number.

Number.isInteger()

Determine whether the passed value is an integer.

Number.isSafeInteger()

Determine whether the passed value is a safe integer (number between -(253 - 1) and 253 - 1).

Number.toInteger()

Used to evaluate the passed value and convert it to an integer (or Infinity), but has been removed.

Number.parseFloat()

The value is the same as parseFloat() of the global object.

Number.parseInt()

The value is the same as parseInt() of the global object.

Number instances

All Number instances inherit from Number.prototype. The prototype object of the Number constructor can be modified to affect all Number instances.

Methods

Number.prototype.toExponential()

Returns a string representing the number in exponential notation.

Number.prototype.toFixed()

Returns a string representing the number in fixed-point notation.

Number.prototype.toLocaleString()

Returns a string with a language sensitive representation of this number. Overrides the Object.prototype.toLocaleString() method.

Number.prototype.toPrecision()

Returns a string representing the number to a specified precision in fixed-point or exponential notation.

Number.prototype.toSource()

Returns an object literal representing the specified Number object; you can use this value to create a new object. Overrides the Object.prototype.toSource() method.

Number.prototype.toString()

Returns a string representing the specified object in the specified radix (base). Overrides the Object.prototype.toString() method.

Number.prototype.valueOf()

Returns the primitive value of the specified object. Overrides the Object.prototype.valueOf() method.

Examples

Using the Number object to assign values to numeric variables

The following example uses the Number object's properties to assign values to several numeric variables:

var biggestNum = Number.MAX_VALUE;
var smallestNum = Number.MIN_VALUE;
var infiniteNum = Number.POSITIVE_INFINITY;
var negInfiniteNum = Number.NEGATIVE_INFINITY;
var notANum = Number.NaN;

Integer range for Number

The following example shows the minimum and maximum integer values that can be represented as Number object (for details, refer to ECMAScript standard, chapter 6.1.6 The Number Type):

var biggestInt = 9007199254740991;
var smallestInt = -9007199254740991;

When parsing data that has been serialized to JSON, integer values falling out of this range can be expected to become corrupted when JSON parser coerces them to Number type. Using String instead is a possible workaround.

Using Number to convert a Date object

The following example converts the Date object to a numerical value using Number as a function:

var d = new Date('December 17, 1995 03:24:00');
console.log(Number(d));

This logs "819199440000".

Convert numeric strings to numbers

Number('123')     // 123
Number('12.3')    // 12.3
Number('')        // 0
Number('0x11')    // 17
Number('0b11')    // 3
Number('0o11')    // 9
Number('foo')     // NaN
Number('100a')    // NaN

Specifications

Browser compatibility

See also

• NaN
• The Math global object
• Number type in details