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
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.
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
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
»
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.
All JavaScript data types have a value Of() and a to String()
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 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:
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
»
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
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
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)
Na N Represents a
"Not-a-Number" value
POSITIVE_INFINITY Represents infinity (returned on overflow)
Example
var x = Number.MAX_VALUE;
Number properties belongs to the JavaScript's number object
wrapper called Number.
These properties can only be accessed as Number. MAX_VALUE.
Using my Number. MAX_VALUE, where my Number is a variable,
expression, or value, will return undefined:
Example
var x = 6;
var y = x.MAX_VALUE; // y becomes undefined
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