JavaScript Core Reference: Number

Lets you work with numeric values. The Number object is an object wrapper for primitive numeric values.

Browser/User Agent Support

IE Mozilla Netscape Opera Safari
3.0+ 1.0+ 3.0+ 7.0+ 1.0+

IE	Mozilla	Netscape	Opera	Safari
3.0+	1.0+	3.0+	7.0+	1.0+

Constructors

Constructor IE Mozilla Netscape Opera Safari
Number Constructor
Creates a new instance of a Number.
3.0+ 1.0+ 3.0+ 7.0+ 1.0+

Constructor	IE	Mozilla	Netscape	Opera	Safari
Number Constructor Creates a new instance of a Number.	3.0+	1.0+	3.0+	7.0+	1.0+

Properties

Property IE Mozilla Netscape Opera Safari
MAX_VALUE
The maximum numeric value representable in JavaScript.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

MIN_VALUE
The smallest positive numeric value representable in JavaScript.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

NaN
A value representing Not-A-Number.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

NEGATIVE_INFINITY
Special value representing negative infinity; returned on overflow.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

POSITIVE_INFINITY
Special value representing infinity; returned on overflow.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

constructor
Specifies the function that creates the Number prototype.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

prototype
Reference to the Number prototype object.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

Property	IE	Mozilla	Netscape	Opera	Safari
MAX_VALUE The maximum numeric value representable in JavaScript.	4.0+	1.0+	3.0+	7.0+	1.0+

MIN_VALUE The smallest positive numeric value representable in JavaScript.	4.0+	1.0+	3.0+	7.0+	1.0+

NaN A value representing Not-A-Number.	4.0+	1.0+	3.0+	7.0+	1.0+

NEGATIVE_INFINITY Special value representing negative infinity; returned on overflow.	4.0+	1.0+	3.0+	7.0+	1.0+

POSITIVE_INFINITY Special value representing infinity; returned on overflow.	4.0+	1.0+	3.0+	7.0+	1.0+

constructor Specifies the function that creates the Number prototype.	4.0+	1.0+	3.0+	7.0+	1.0+

prototype Reference to the Number prototype object.	4.0+	1.0+	3.0+	7.0+	1.0+

Methods

Method IE Mozilla Netscape Opera Safari
toExponential
Returns a string representing the number in exponential notation.
5.5+ 1.0+ 6.0+ 7.0+ 1.0+

toFixed
Returns a string representing the number in fixed-point notation.
5.5+ 1.0+ 6.0+ 7.0+ 1.0+

toLocaleString
Returns a string representing the number that follows local formatting conventions.
5.5+ 1.0+ 6.0+ 7.0+ 1.0+

toPrecision
Returns a string representing the number to a specified precision in fixed-point notation.
5.5+ 1.0+ 6.0+ 7.0+ 1.0+

toSource
Returns an object literal representing the specified Number object; you can use this value to create a new object.
4.0+ 1.0+ 3.0+ no no

toString
Returns a string representing the specified object.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

valueOf
Returns the primitive value of the specified object.
4.0+ 1.0+ 3.0+ 7.0+ 1.0+

Method	IE	Mozilla	Netscape	Opera	Safari
toExponential Returns a string representing the number in exponential notation.	5.5+	1.0+	6.0+	7.0+	1.0+

toFixed Returns a string representing the number in fixed-point notation.	5.5+	1.0+	6.0+	7.0+	1.0+

toLocaleString Returns a string representing the number that follows local formatting conventions.	5.5+	1.0+	6.0+	7.0+	1.0+

toPrecision Returns a string representing the number to a specified precision in fixed-point notation.	5.5+	1.0+	6.0+	7.0+	1.0+

toSource Returns an object literal representing the specified Number object; you can use this value to create a new object.	4.0+	1.0+	3.0+	no	no

toString Returns a string representing the specified object.	4.0+	1.0+	3.0+	7.0+	1.0+

valueOf Returns the primitive value of the specified object.	4.0+	1.0+	3.0+	7.0+	1.0+

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:

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

Using `Number` object to modify all `Number` objects

The following example creates a Number object, myNum, then adds a description property to all Number objects. Then a value is assigned to the myNum object's description property.

myNum = new Number(65);
Number.prototype.description = null;
myNum.description = "wind speed";

Remarks

The primary uses for the Number object are:

To access its constant properties, which represent the largest and smallest representable numbers, positive and negative infinity, and the Not-a-Number value.

To create numeric objects that you can add properties to. Most likely, you will rarely need to create a Number object.

The properties of Number are properties of the class itself, not of individual Number objects.

JavaScript 1.2: Number(x) now produces NaN rather than an error if x is a string that does not contain a well-formed numeric literal. For example, the following prints NaN:

x=Number("three");
document.write(x + "<BR>");

You can convert any object to a number using the top-level Number function.

References

Global.Infinity | Math | Global.NaN

Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1

Constructor Detail

Number Number(Number value)

Creates a new instance of a Number.

Number value The numeric value of the object being created.

Property Detail

static Number MAX_VALUE - read only

The maximum numeric value representable in JavaScript.

Using `MAX_VALUE`

The following code multiplies two numeric values. If the result is less than or equal to MAX_VALUE, the func1 function is called; otherwise, the func2 function is called.

if (num1 * num2 <= Number.MAX_VALUE)
   func1();
else
   func2();

Remarks

The MAX_VALUE property has a value of approximately 1.79E+308. Values larger than MAX_VALUE are represented as "Infinity".

Because MAX_VALUE is a static property of Number, you always use it as Number.MAX_VALUE, rather than as a property of a Number object you created.

Availability

JavaScript 1.1 | JScript 2.0, ECMAScript v1

static Number MIN_VALUE - read only

The smallest positive numeric value representable in JavaScript.

Using `MIN_VALUE`

The following code divides two numeric values. If the result is greater than or equal to MIN_VALUE, the func1 function is called; otherwise, the func2 function is called.

if (num1 / num2 >= Number.MIN_VALUE)
   func1()
else
   func2()

Remarks

The MIN_VALUE property is the number closest to 0, not the most negative number, that JavaScript can represent.

MIN_VALUE has a value of approximately 5e-324. Values smaller than MIN_VALUE ("underflow values") are converted to 0.

Because MIN_VALUE is a static property of Number, you always use it as Number.MIN_VALUE, rather than as a property of a Number object you created.

Availability

JavaScript 1.1 | JScript 2.0, ECMAScript v1

static Number NaN - read only

A value representing Not-A-Number.

Using `NaN`

In the following example, if month has a value greater than 12, it is assigned NaN, and a message is displayed indicating valid values.

var month = 13
if (month < 1 || month > 12) {
   month = Number.NaN
   alert("Month must be between 1 and 12.")
}

Remarks

The value of Number.NaN is Not-A-Number, same as the value of global object's NaN property.

NaN is always unequal to any other number, including NaN itself; you cannot check for the not-a-number value by comparing to Number.NaN. Use the isNaN function instead.

Several JavaScript methods (such as the Number constructor, parseFloat, and parseInt) return NaN if the value specified in the parameter can not be parsed as a number.

You might use the NaN property to indicate an error condition for your function that returns a number in case of success.

JavaScript prints the value Number.NaN as NaN.

Availability

JavaScript 1.1 | JScript 2.0, ECMAScript v1

static Number NEGATIVE_INFINITY - read only

Special value representing negative infinity; returned on overflow.

See Also: Global.Infinity | isFinite
Availability: JavaScript 1.1 | JScript 2.0, ECMAScript v1

static Number POSITIVE_INFINITY - read only

Special value representing infinity; returned on overflow.

See Also: Global.Infinity | isFinite
Availability: JavaScript 1.1 | JScript 2.0, ECMAScript v1

Object constructor - only

Specifies the function that creates the Number prototype.

See Also: Object.constructor
Availability: JavaScript 1.1

Object prototype - only

Reference to the Number prototype object.

Availability: JavaScript 1.1

Method Detail

toExponential([Number digits]) : String

Returns a string representing the number in exponential notation.

Number digits Number of decimal places to appear after the decimal point. (optional)

Throws

Throws RangeError if digits is too small or too large of a number.

Throws TypeError if the method is invoked on an object that is not a Number.

Availability

JavaScript 1.5 | JScript 5.5, ECMAScript v3

toFixed([Number digits]) : String

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

Number digits Number of decimal places to appear after the decimal point. (optional)

Throws

Throws RangeError if digits is too small or too large of a number.

Throws TypeError if the method is invoked on an object that is not a Number.

Availability

JavaScript 1.5 | JScript 5.5, ECMAScript v3

toLocaleString() : String

Returns a string representing the number that follows local formatting conventions.

Throws

Throws TypeError if the method is invoked on an object that is not a Number.

Availability

JavaScript 1.5 | JScript 5.5, ECMAScript v3

toPrecision([String precision]) : String

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

String precision The number of significant digits to use in the returned string. (optional)

Throws

Throws RangeError if digits is too small or too large of a number.

Throws TypeError if the method is invoked on an object that is not a Number.

Availability

JavaScript 1.5 | JScript 5.5, ECMAScript v3

toSource() : Object

Returns an object literal representing the specified Number object; you can use this value to create a new object.

Availability

toString([Number radix]) : String

Returns a string representing the specified object.

Number radix The radix (or base) between 2 and 36 to use to represent the number. (optional)

Throws

Throws TypeError if the method is invoked on an object that is not a Number.

Availability

JavaScript 1.1 | JScript 2.0, ECMAScript v1

valueOf() : Number

Returns the primitive value of the specified object.

Throws

Throws TypeError if the method is invoked on an object that is not a Number.

See Also

Object.valueOf

Availability

JavaScript 1.1 | JScript 2.0, ECMAScript v1

Number : Object

Browser/User Agent Support

Constructors

Properties

Methods

Using the Number object to assign values to numeric variables

Using Number object to modify all Number objects

Remarks

References

Availability

Constructor Detail

Number Number(Number value)

Property Detail

static Number MAX_VALUE - read only

Using MAX_VALUE

static Number MIN_VALUE - read only

Using MIN_VALUE

static Number NaN - read only

Using NaN

static Number NEGATIVE_INFINITY - read only

static Number POSITIVE_INFINITY - read only

Object constructor - only

Object prototype - only

Method Detail

toExponential([Number digits]) : String

toFixed([Number digits]) : String

toLocaleString() : String

toPrecision([String precision]) : String

toSource() : Object

toString([Number radix]) : String

valueOf() : Number

Using the `Number` object to assign values to numeric variables

Using `Number` object to modify all `Number` objects

Using `MAX_VALUE`

Using `MIN_VALUE`

Using `NaN`