JavaScript Number Methods

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

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

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

EXAMPLE ❯


                                let x = 123;<br />
x.toString();            // returns 123 from variable x<br />
(123).toString();        // returns 123 from literal 123<br />
(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.

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

EXAMPLE ❯


                                let x = 9.656;<br />
x.toExponential(2);     // returns 9.66e+0<br />
x.toExponential(4);     // returns 9.6560e+0<br />
x.toExponential(6);     // returns 9.656000e+0

The toFixed() Method

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

EXAMPLE ❯


                                let x = 9.656;<br />
x.toFixed(0);           // returns 10<br />
x.toFixed(2);           // returns 9.66<br />
x.toFixed(4);           // returns 9.6560<br />
x.toFixed(6);           // returns 9.656000

toFixed(2) is perfect for working with money.

The toPrecision() Method

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

EXAMPLE ❯


                                let x = 9.656;<br />
x.toPrecision();        // returns 9.656<br />
x.toPrecision(2);       // returns 9.7<br />
x.toPrecision(4);       // returns 9.656<br />
x.toPrecision(6);       // returns 9.65600

The valueOf() Method

valueOf() returns a number as a number.

EXAMPLE ❯


                                let x = 123;<br />
x.valueOf();            // returns 123 from variable x<br />
(123).valueOf();        // returns 123 from literal 123<br />
(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 JavaScript 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:

If the number cannot be converted, NaN (Not a Number) is returned.

EXAMPLE ❯


                                Number(true);          // returns 1<br />
Number(false);         // returns 0<br />
Number("10");          // returns 10<br />
Number("  10");        // returns 10<br />
Number("10  ");        // returns 10<br />
Number(" 10  ");       // returns 10<br />
Number("10.33");       // returns 10.33<br />
Number("10,33");       // returns NaN<br />
Number("10 33");       // returns NaN<br />
Number("John");        // returns NaN

The Number() Method Used on Dates

Number() can also convert a date to a number.

EXAMPLE ❯


                                // This returns 0:<br />
Number(new Date("1970-01-01"))

EXAMPLE ❯


                                // This returns 86400000<br />
Number(new Date("1970-01-02"))

EXAMPLE ❯


                                // This returns 1506729600000<br />
Number(new Date("2017-09-30"))

The parseInt() Method

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

If the number cannot be converted, NaN (Not a Number) is returned.

EXAMPLE ❯


                                parseInt("-10");        // returns -10<br />
parseInt("-10.33");     // returns -10<br />
parseInt("10");         // returns 10<br />
parseInt("10.33");      // returns 10<br />
parseInt("10 20 30");   // returns 10<br />
parseInt("10 years");   // returns 10<br />
parseInt("years 10");   // returns NaN

The parseFloat() Method

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

If the number cannot be converted, NaN (Not a Number) is returned.

EXAMPLE ❯


                                parseFloat("10");        // returns 10<br />
parseFloat("10.33");     // returns 10.33<br />
parseFloat("10 20 30");  // returns 10<br />
parseFloat("10 years");  // returns 10<br />
parseFloat("years 10");  // returns NaN

Number Properties

Property	Description
MAX_VALUE	Returns the largest number possible in JavaScript
MIN_VALUE	Returns the smallest number possible in JavaScript
POSITIVE_INFINITY	Represents infinity (returned on overflow)
NEGATIVE_INFINITY	Represents negative infinity (returned on overflow)
NaN	Represents a "Not-a-Number" value

JavaScript MIN_VALUE and MAX_VALUE

MAX_VALUE returns the largest possible number in JavaScript.

EXAMPLE ❯


                                let x = Number.MAX_VALUE;

MIN_VALUE returns the lowest possible number in JavaScript.

EXAMPLE ❯


                                let x = Number.MIN_VALUE;

JavaScript POSITIVE_INFINITY

EXAMPLE ❯


                                let x = Number.POSITIVE_INFINITY;

POSITIVE_INFINITY is returned on overflow:

EXAMPLE ❯


                                let x = 1 / 0;

JavaScript NEGATIVE_INFINITY

EXAMPLE ❯


                                let x = Number.NEGATIVE_INFINITY;

NEGATIVE_INFINITY is returned on overflow:

EXAMPLE ❯


                                let x = -1 / 0;

JavaScript NaN - Not a Number

EXAMPLE ❯


                                let x = Number.NaN;

NaN is a JavaScript reserved word indicating that a number is not a legal number.

Trying to do arithmetic with a non-numeric string will result in NaN (Not a Number):

EXAMPLE ❯


                                let x = 100 / "Apple";  // x will be NaN (Not a Number)

Number Properties Cannot be Used on Variables

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 ❯


                                let x = 6;<br />
x.MAX_VALUE    // returns undefined

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Tutorial

JavaScript Number Methods

Number Methods and Properties

The toString() Method

EXAMPLE ❯

The toExponential() Method

EXAMPLE ❯

The toFixed() Method

EXAMPLE ❯

The toPrecision() Method

EXAMPLE ❯

The valueOf() Method

EXAMPLE ❯

Converting Variables to Numbers

Global JavaScript Methods

The Number() Method

EXAMPLE ❯

The Number() Method Used on Dates

EXAMPLE ❯

EXAMPLE ❯

EXAMPLE ❯

The parseInt() Method

EXAMPLE ❯

The parseFloat() Method

EXAMPLE ❯

Number Properties

JavaScript MIN_VALUE and MAX_VALUE

EXAMPLE ❯

MIN_VALUE returns the lowest possible number in JavaScript.

EXAMPLE ❯

JavaScript POSITIVE_INFINITY

EXAMPLE ❯

EXAMPLE ❯

JavaScript NEGATIVE_INFINITY

EXAMPLE ❯

EXAMPLE ❯

JavaScript NaN - Not a Number

EXAMPLE ❯

EXAMPLE ❯

Number Properties Cannot be Used on Variables

EXAMPLE ❯