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JavaScript Number Methods


Numbers methods help you to work with numbers.


Global Methods

JavaScript global functions 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


Number Methods

JavaScript number methods are methods that can be used on numbers:

Method Description
toString() Returns a number as a string
toExponential() Returns a string, with a number rounded and written using exponential notation.
toFixed() Returns a string, with a number rounded and written with a specified number of decimals.
toPrecision() Returns a string, with a number written with a specified length
valueOf() Returns a number as a number

Note All number methods return a new variable. They do not change the original variable.


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

Try it yourself »


The toExponential() Method

toExponential() returns a string, with a number rounded and written using exponential notation.

A parameter defines the number of character 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 »

Note 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

Try it yourself »


Converting Variables to Numbers

There are 3 JavaScript functions 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.


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

Try it yourself »


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.


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

Try it yourself »

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.

Note In JavaScript, all data types have a valueOf() and a toString() method.


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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