Book Image

Object-Oriented JavaScript

By : Stoyan Stefanov, Stoyan STEFANOV
Book Image

Object-Oriented JavaScript

By: Stoyan Stefanov, Stoyan STEFANOV

Overview of this book

Table of Contents (18 chapters)
Object-Oriented JavaScript
Credits
About the Author
About the Reviewers
Preface
Built-in Functions
Regular Expressions
Index

Math


Math is a little different from the other built-in objects, because it cannot be used as a constructor to create objects. It is just a collection of functions and constants. Some examples, to illustrate the difference, are given below:

>>> typeof String.prototype

"object"

>>> typeof Date.prototype

"object"

>>> typeof Math.prototype

"undefined"

>>> typeof Math

"object"

>>> typeof String

"function"

Members of the Math Object

Property/Method

Description

Math.E

Math.LN10

Math.LN2

Math.LOG2E

Math.LOG10E

Math.PI

Math.SQRT1_2

Math.SQRT2

These are some useful math constants, all read-only. Here are their values:

>>> Math.E

2.718281828459045

>>> Math.LN10

2.302585092994046

>>> Math.LN2

0.6931471805599453

>>> Math.LOG2E

1.4426950408889634

>>> Math.LOG10E

0.4342944819032518

>>> Math.PI

3.141592653589793

>>> Math.SQRT1_2

0.7071067811865476

>>> Math.SQRT2

1.4142135623730951

Math.acos(x)

Math.asin(x)

Math.atan(x)

Math.atan2(y, x)

Math.cos(x)

Math.sin(x)

Math.tan(x)

Trigonometric functions

Math.round(x)

Math.floor(x)

Math.ceil(x)

round() gives you the nearest integer, ceil() rounds up and floor() rounds down:

>>> Math.round(5.5)

6

>>> Math.floor(5.5)

5

>>> Math.ceil(5.1)

6

Math.max(num1, num2, num3, ...)

Math.min(num1, num2, num3, ...)

max() returns the largest and min() returns the smallest of the numbers passed to them as arguments. If at least one of the input parameters is NaN, the result is also NaN.

>>> Math.max(2, 101, 4.5)

101

>>> Math.min(2, 101, 4.5)

2

Math.abs(x)

Absolute value.

>>> Math.abs(-101)

101

>>> Math.abs(101)

101

Math.exp(x)

Exponential function: Math.E to the power of x

Math.log(x)

Natural logarithm of x.

Math.sqrt(x)

Square root of x .

>>> Math.sqrt(9)

3

>>> Math.sqrt(2) === Math.SQRT2

true

Math.pow(x, y)

x to the power of y.

>>> Math.pow(3, 2)

9

Math.random()

Random number between 0 and 1 (including 0).

>>> Math.random()

0.8279076443185321