JavaScript Number Methods

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JavaScript Number Methods
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Number methods help you work with numbers.

Number Methods and Properties
Primitive values (like 3.14 or 2014), cannot have properties and methods (because they are not objects).

But with JavaScript, methods and properties are also available to primitive values, because JavaScript treats primitive values as objects when executing methods and properties.

The toString() Method
toString() returns a number as a string.

All number methods can be used on any type of numbers (literals, variables, or expressions):

Example
var x = 123;
x.toString();            // returns 123 from variable x
(123).toString();        // returns 123 from literal 123
(100 + 23).toString();   // returns 123 from expression 100 + 23
»
The toExponential() Method
toExponential() returns a string, with a number rounded and written using exponential notation.

A parameter defines the number of characters behind the decimal point:

Example
var x = 9.656;
x.toExponential(2);     // returns 9.66e+0
x.toExponential(4);     // returns 9.6560e+0
x.toExponential(6);     // returns 9.656000e+0
Try it yourself »
The parameter is optional. If you don't specify it, JavaScript will not round the number.

The toFixed() Method
toFixed() returns a string, with the number written with a specified number of decimals:

Example
var x = 9.656;
x.toFixed(0);           // returns 10
x.toFixed(2);           // returns 9.66
x.toFixed(4);           // returns 9.6560
x.toFixed(6);           // returns 9.656000
Try it yourself »
toFixed(2) is perfect for working with money.

The toPrecision() Method
toPrecision() returns a string, with a number written with a specified length:

Example
var x = 9.656;
x.toPrecision();        // returns 9.656
x.toPrecision(2);       // returns 9.7
x.toPrecision(4);       // returns 9.656
x.toPrecision(6);       // returns 9.65600
»
The valueOf() Method
valueOf() returns a number as a number.

Example
var x = 123;
x.valueOf();            // returns 123 from variable x
(123).valueOf();        // returns 123 from literal 123
(100 + 23).valueOf();   // returns 123 from expression 100 + 23
»
In JavaScript, a number can be a primitive value (typeof = number) or an object (typeof = object).

The valueOf() method is used internally in JavaScript to convert Number objects to primitive values.

There is no reason to use it in your code.

All JavaScript data types have a valueOf() and a toString() method.

Converting Variables to Numbers
There are 3 JavaScript methods that can be used to convert variables to numbers:

The Number() method
The parseInt() method
The parseFloat() method
These methods are not number methods, but global JavaScript methods.

Global Methods
JavaScript global methods can be used on all JavaScript data types.

These are the most relevant methods, when working with numbers:

Method Description
Number() Returns a number, converted from its argument.
parseFloat() Parses its argument and returns a floating point number
parseInt() Parses its argument and returns an integer
The Number() Method
Number() can be used to convert JavaScript variables to numbers:

Example
x = true;
Number(x);        // returns 1
x = false;    
Number(x);        // returns 0
x = new Date();
Number(x);        // returns 1404568027739
x = "10"
Number(x);        // returns 10
x = "10 20"
Number(x);        // returns NaN
»
Used on Date(), the Number() method returns the number of milliseconds since 1.1.1970.

The parseInt() Method
parseInt() parses a string and returns a whole number. Spaces are allowed. Only the first number is returned:

Example
parseInt("10");         // returns 10
parseInt("10.33");      // returns 10
parseInt("10 20 30");   // returns 10
parseInt("10 years");   // returns 10
parseInt("years 10");   // returns NaN
Try it yourself »
If the number cannot be converted, NaN (Not a Number) is returned.

The parseFloat() Method
parseFloat() parses a string and returns a number. Spaces are allowed. Only the first number is returned:

Example
parseFloat("10");        // returns 10
parseFloat("10.33");     // returns 10.33
parseFloat("10 20 30");  // returns 10
parseFloat("10 years");  // returns 10
parseFloat("years 10");  // returns NaN
Try it yourself »
If the number cannot be converted, NaN (Not a Number) is returned.

Number Properties
Property Description
MAX_VALUE Returns the largest number possible in JavaScript
MIN_VALUE Returns the smallest number possible in JavaScript
NEGATIVE_INFINITY Represents negative infinity (returned on overflow)
NaN Represents a "Not-a-Number" value
POSITIVE_INFINITY Represents infinity (returned on overflow)
Example
var x = Number.MAX_VALUE;
Try it yourself »
Number properties belongs to the JavaScript's number object wrapper called Number.

These properties can only be accessed as Number.MAX_VALUE.

Using myNumber.MAX_VALUE, where myNumber is a variable, expression, or value, will return undefined:

Example
var x = 6;
var y = x.MAX_VALUE;    // y becomes undefined
Try it yourself »
Complete JavaScript Number Reference
For a complete reference, go to our Complete JavaScript Number Reference.

The reference contains descriptions and examples of all Number properties and methods.


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