W3cubDocs

/JavaScript

Number

Number is a primitive wrapper object used to represent and manipulate numbers like 37 or -9.25.

The Number constructor contains constants and methods for working with numbers. Values of other types can be converted to numbers using theNumber().

The JavaScript Number type is a double-precision 64-bit binary format IEEE 754 value, like double in Java or C#. This means it can represent fractional values, but there are some limits to what it can store. A Number only keeps about 17 decimal places of precision; arithmetic is subject to rounding. The largest value a Number can hold is about 1.8×10308. Numbers beyond that are replaced with the special Number constant Infinity.

A number literal like 37 in JavaScript code is a floating-point value, not an integer. There is no separate integer type in common everyday use. (JavaScript now has a BigInt type, but it was not designed to replace Number for everyday uses. 37 is still a Number, not a BigInt.)

Number may also be expressed in literal forms like 0b101, 0o13, 0x0A. Learn more on numeric lexical grammar here.

Description

When used as a function, Number(value) converts a string or other value to the Number type. If the value can't be converted, it returns NaN.

Literal syntax

123    // one-hundred twenty-three
123.0  // same
123 === 123.0  // true

Function syntax

Number('123')  // returns the number 123
Number('123') === 123  // true

Number("unicorn")  // NaN
Number(undefined)  // NaN

Constructor

Number()
Creates a new Number value.

Static 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 the Number object.

Static 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.parseFloat(string)
This is the same as the global parseFloat() function.
Number.parseInt(string, [radix])
This is the same as the global parseInt() function.

Instance methods

Number.prototype.toExponential(fractionDigits)
Returns a string representing the number in exponential notation.
Number.prototype.toFixed(digits)
Returns a string representing the number in fixed-point notation.
Number.prototype.toLocaleString([locales [, options]])
Returns a string with a language sensitive representation of this number. Overrides the Object.prototype.toLocaleString() method.
Number.prototype.toPrecision(precision)
Returns a string representing the number to a specified precision in fixed-point or exponential notation.
Number.prototype.toString([radix])
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:

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

Integer range for Number

The following example shows the minimum and maximum integer values that can be represented as Number object. (More details on this are described in the ECMAScript standard, chapter 6.1.6 The Number Type.)

const biggestInt  = Number.MAX_SAFE_INTEGER  //  (253 - 1) =>  9007199254740991
const smallestInt = Number.MIN_SAFE_INTEGER  // -(253 - 1) => -9007199254740991

When parsing data that has been serialized to JSON, integer values falling outside of this range can be expected to become corrupted when JSON parser coerces them to Number type.

A possible workaround is to use String instead.

Larger numbers can be represented using the BigInt type.

Using Number to convert a Date object

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

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

This logs 819199440000.

Convert numeric strings and null to numbers

Number('123')     // 123
Number('123') === 123 /// true
Number('12.3')    // 12.3
Number('12.00')   // 12
Number('123e-1')  // 12.3
Number('')        // 0
Number(null)      // 0
Number('0x11')    // 17
Number('0b11')    // 3
Number('0o11')    // 9
Number('foo')     // NaN
Number('100a')    // NaN
Number('-Infinity') //-Infinity

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Number 1 12 1 3 3 1
EPSILON 34 12 25 No 21 9
MAX_SAFE_INTEGER 34 12 31 No 21 9
MAX_VALUE 1 12 1 4 3 1
MIN_SAFE_INTEGER 34 12 31 No 21 9
MIN_VALUE 1 12 1 4 3 1
NaN 1 12 1 4 3 1
NEGATIVE_INFINITY 1 12 1 4 3 1
Number() constructor 1 12 1 3 3 1
POSITIVE_INFINITY 1 12 1 4 3 1
isFinite 19 12 16 No 15 9
isInteger 34 12 16 No 21 9
isNaN 25 12 15 No 15 9
isSafeInteger 34 12 32 No 21 10
parseFloat 34 12 25 No 21 9
parseInt 34 12 25 No 21 9
toExponential 1 12 1 5.5 7 2
toFixed 1 12 1 5.5 7 2
toLocaleString 1 12
12
Before Edge 18, numbers are rounded to 15 decimal digits. For example, (1000000000000005).toLocaleString('en-US') returns "1,000,000,000,000,010".
1 5
5
In Internet Explorer 11, numbers are rounded to 15 decimal digits. For example, (1000000000000005).toLocaleString('en-US') returns "1,000,000,000,000,010".
4 1
toPrecision 1 12 1 5.5 7 2
toSource No No 1 — 74
1 — 74
Starting in Firefox 74, toSource() is no longer available for use by web content. It is still allowed for internal and privileged code.
No No No
toString 1 12 1 3 4 1
valueOf 1 12 1 4 4 1
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
Number 1 18 4 10.1 1 1.0
EPSILON ≤37 34 25 21 9 2.0
MAX_SAFE_INTEGER ≤37 34 31 21 9 2.0
MAX_VALUE 1 18 4 10.1 1 1.0
MIN_SAFE_INTEGER ≤37 34 31 21 9 2.0
MIN_VALUE 1 18 4 10.1 1 1.0
NaN 1 18 4 10.1 1 1.0
NEGATIVE_INFINITY 1 18 4 10.1 1 1.0
Number() constructor 1 18 4 10.1 1 1.0
POSITIVE_INFINITY 1 18 4 10.1 1 1.0
isFinite ≤37 25 16 14 9 1.5
isInteger ≤37 34 16 21 9 2.0
isNaN ≤37 25 15 14 9 1.5
isSafeInteger ≤37 34 32 21 10 2.0
parseFloat ≤37 34 25 21 9 2.0
parseInt ≤37 34 25 21 9 2.0
toExponential 1 18 4 10.1 1 1.0
toFixed 1 18 4 10.1 1 1.0
toLocaleString 1 18 4 10.1 1 1.0
toPrecision 1 18 4 10.1 1 1.0
toSource No No 4 No No No
toString 1 18 4 10.1 1 1.0
valueOf 1 18 4 10.1 1 1.0
Server
Node.js
Number 0.1.100
EPSILON 0.12
MAX_SAFE_INTEGER 0.12
MAX_VALUE 0.1.100
MIN_SAFE_INTEGER 0.12
MIN_VALUE 0.1.100
NaN 0.1.100
NEGATIVE_INFINITY 0.1.100
Number() constructor 0.1.100
POSITIVE_INFINITY 0.1.100
isFinite 0.10
isInteger 0.12
isNaN 0.10
isSafeInteger 0.12
parseFloat 0.12
parseInt 0.12
toExponential 0.1.100
toFixed 0.1.100
toLocaleString 0.1.100
toPrecision 0.1.100
toSource No
toString 0.1.100
valueOf 0.1.100

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number