JavaScript Numbers Methods

Number methods can help you when working with number datatypes. The number methods are improved in ES6 (ECMAScript 6).

Keep reading to understand how the number methods and properties may help you.


JavaScript Convert Variable to Number

There are 3 important JavaScript methods that can convert a variable to a number. 

The methods are global JavaScript methods and not number methods. JavaScript global methods can be used on all JavaScript data types.

The methods are:Number() parseInt() parseFloat()


Method Description

Number()

Convert a variable to a number.

parseInt()

Convert a variable to an integer. (whole number without decimal point)

parseFloat()

Convert a string variable to number with or without decimal point.


Learn more about JavaScript Numbers

The Number() Method

The Number() method can convert JavaScript variables to numbers.

NaN (Not a Number) is returned if the variable cannot be converted to a number.

Number(true);             // returns 1
Number(false);            // returns 0
Number("8");              // returns 8
Number(" 8  ");           // returns 8
Number("  8");            // returns 8
Number("8  ");            // returns 8
Number("8.48");           // returns 8.48
Number("8,48");           // returns NaN
Number("8 48");           // returns NaN 
Number("Donald");         // returns NaN

The Number() Method Convert a Date

The Number() method can also convert a date to a number

var date = new Date("2018-08-08");
// Date converted to number since 01.01.1970
alert("Date: " + date + "\n\nConverted to number: " + Number(date)); 

Learn more about JavaScript Dates

The ParseInt Method

The parseInt() method parses a string and returns a number. Spaces are allowed and only the first number is returned.

NaN (Not a Number) is returned if the number can not be converted.

parseInt("88");         // returns 88
parseInt("88.20");      // returns 88
parseInt("88 89 90");   // returns 88
parseInt("88 days");    // returns 88
parseInt("Day 88");     // returns NaN  

The parseFloat() Method

The parseFloat() method parses a string and returns a floating point number. Spaces are allowed and only the first number is returned.

NaN (Not a Number) is returned if the number can not be converted.

parseFloat("88");         // returns 88
parseFloat("88.20");      // returns 88.20
parseFloat("88 89 90");   // returns 88
parseFloat("88 days");    // returns 88
parseFloat("Day 88");     // returns NaN  

Number Format Methods

JavaScript have some number format methods that are specifically used on numbers.

The methods are:
toString() toExponential() toFixed() toPrecision() valueOf()


Method Description

toString()

Return number as string.

toExponential()

Return string, with number rounded and written with exponential notation.

toFixed()

Return string, with number rounded and written using a specified number of decimals.

toPrecision()

Return string, with a number written with a specified length.

valueOf()

Return number as number.


Number Format - The toString() Method

The toString()method returns a number as a string. (a sequence of characters). All JavaScript number format methods can be used with literals, variables or expressions.

var a = 88;  
a.toString();            // return 88 from variable a 
(88).toString();         // return 88 from literal 88  
(80 + 8).toString();     // return 88 from expression 80 + 8


Number Format - The toExponential() Method

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

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

var x = 8;  
x.toExponential(2);    // return 8.00e+0 
x.toExponential(4);    // return 8.0000e+0  
x.toExponential(6);    // return 8.000000e+0

Number Format - The toFixed() Method

The toFixed() method returns a string, with the number written with a specified number of decimals.

var x = 8.2468;  
x.toFixed(0);           // return 8  
x.toFixed(2);           // return 8.2 
x.toFixed(4);           // return 8.2468
x.toFixed(6);           // return 8.24680

Number Format - The toPrecision() Method

The toPrecision() method returns a string, with a number written with a specified length.

var x = 8.248;  
x.toPrecision();        // return 8.248
x.toPrecision(2);       // return 8.2  
x.toPrecision(4);       // return 8.248 
x.toPrecision(6);       // return 8.24800

Number Format - The valueOf() Method

The valueOf() method returns a number as a number.

This method is used internally to turn Number objects into primitive values. Normally you don’t need to use this function.

var x = 84; 
x.valueOf();            // return 84 from variable x 
(84).valueOf();         // return 84 from literal 84  
(100 + 84).valueOf();   // return 184 from expression 100 + 84

Number Properties

There is a list of static properties available on the Number object.
Property Description

MAX_VALUE

Return the largest number possible in JavaScript.

MIN_VALUE

Return the smallest number possible in JavaScript.

POSITIVE_INFINITY

Represent infinity (returned on overflow).

NEGATIVE_INFINITY

Represent negative infinity (returned on overflow).

NaN

Represent a "Not-a-Number" value.


Learn more about JavaScript Arithmetics Learn more about JavaScript Assignment

Number Properties Examples

// MAX_VALUE - the largest number possible in JavaScript
alert('MAX_VALUE: ' + Number.MAX_VALUE);
 
// MIN_VALUE - the smallest number possible in JavaScript
alert('MAX_VALUE: ' + Number.MIN_VALUE); 
 
// POSITIVE_INFINITY - Return Infinity
alert('POSITIVE_INFINITY: ' + Number.POSITIVE_INFINITY);
 
// NEGATIVE_INFINITY - Return -Infinity 
alert('NEGATIVE_INFINITY: ' + Number.NEGATIVE_INFINITY);
 
// NaN - Return NaN
alert('NaN: ' + Number.NaN);

Number Properties On Variables

It is not possible to use the number properties on variables. Using number properties on variables will return undefined.

var a = 88;
var b = a.MAX_VALUE;    // b becomes undefined 

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