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 the Number()
function.
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 1.8E308. Values higher than 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 (
2^53 - 1
). Number.MAX_VALUE
-
The largest positive representable number.
Number.MIN_SAFE_INTEGER
-
The minimum safe integer in JavaScript (
-(2^53 - 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
-(2^53 - 1)
and2^53 - 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 // (2**53 - 1) => 9007199254740991
const smallestInt = Number.MIN_SAFE_INTEGER // -(2**53 - 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
Specification |
---|
ECMAScript Language Specification # sec-number-objects |
Browser compatibility
BCD tables only load in the browser
See also
- Polyfill of modern
Number
behavior (with support binary and octal literals) incore-js
NaN
- Arithmetic operators
- The
Math
global object - Integers with arbitrary precision:
BigInt