JavaScript Number Methods

Number methods help you to work with numbers.

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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

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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

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

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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 

 

The parameter is optional. If you don't specify it, JavaScript will not round the number.

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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 

 

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 

 

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.

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The Number() Method

Number(), can be used to convert JavaScript variables to numbers:

Example

x = true;
Number(x);        // returns 1x = false;    
Number(x);        // returns 0x = new Date();
Number(x);        // returns 1404568027739 x = "10"
Number(x);        // returns 10 x = "10 20"
Number(x);        // returns NaN 

 

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 10parseInt("years 10");   // returns NaN 

  

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 10parseFloat("years 10");  // returns NaN 

 

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.

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