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
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 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
Try it Yourself
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.
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:
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:
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
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) |
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:
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.