The Math Object

The Math Object

The Math object gives you access to powerful math routines, such as log , sqrt , and pow (which raises values to various powers). We've already seen the Math object in the book every now and then when we had to round off numbers or find absolute values. You can see the properties (actually, they're read-only constants, which is why they're all in capital letters ) and methods of the Math object in Table 19.1, its properties in depth in Table 19.2, and its methods in Table 19.3.

Tip

The trig methods of the Math object take or return radian values. To convert an angle in degrees to radians, multiply that angle by pi and divide by 180.

Table 19.1. Overview of the Properties and Methods of the Math Object

Properties	Methods
E	abs
LN2	acos
LN10	asin
LOG2E	atan
LOG10E	atan2
PI	ceil
SQRT1_2	cos
SQRT2	exp
	floor
	log
	max
	min
	pow
	random
	round
	sin
	sqrt
	tan

Table 19.2. The Properties of the Math Object

Property	NS2	NS3	NS4	NS6	IE3a	IE3b	IE4	IE5	IE5.5	IE6
E	x	x	x	x	x	x	x	x	x	x
	Read-only
	The natural log constant e, stored in JavaScript as 2.718281828459045091.
LN2	x	x	x	x	x	x	x	x	x	x
	Read-only
	The natural log of 2, stored in JavaScript as 0.6931471805599452862.
LN10	x	x	x	x	x	x	x	x	x	x
	Read-only
	The natural log of 10, stored in JavaScript as 2.302585092994045901.
LOG2E	x	x	x	x	x	x	x	x	x	x
	Read-only
	The base 2 log of e, stored in JavaScript as 1.442695040888963387.
LOG10E	x	x	x	x	x	x	x	x	x	x
	Read-only
	The base 10 log of e, stored in JavaScript as 0.4342944819032518167.
PI	x	x	x	x	x	x	x	x	x	x
	Read-only
	Pi, stored in JavaScript as 3.141592653589793116.
SQRT1_2	x	x	x	x	x	x	x	x	x	x
	Read-only
	The square root of one half, stored in JavaScript as 0.7071067811865475727.
SQRT2	x	x	x	x	x	x	x	x	x	x
	Read-only
	The square root of 2, stored in JavaScript as 1.414213562373095145.

Table 19.3. The Methods of the Math Object

Method	NS2	NS3	NS4	NS6	IE3a	IE3b	IE4	IE5	IE5.5	IE6
Eabs	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the absolute value of a number.
	Syntax: Math.abs( value ) , where value is the number for which you want the absolute value.
acos	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the arc cosine of a value, in radians.
	Syntax: Math.acos( value ) , where value is the value for which you want the arc cosine.
asin	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the arc sine of a value, in radians.
	Syntax: Math.asin( value ) , where value is the value for which you want the arc sine.
atan	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the arc tangent of a value, in radians.
	Syntax: Math.atan( value ) , where value is the value for which you want the arc tangent.
atan2	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the angle (in radians) from the X axis to a point ( y , x ).
	Syntax: Math.atan2( y , x ) .
ceil	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the smallest integer greater than or equal to the value you pass.
	Syntax: Math.ceil( value ) , where value is the value you want to round up.
cos	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the cosine of a value.
	Syntax: Math.cos( value ) , where value is the value, in radians, for which you want the cosine.
exp	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns e to the power you specify.
	Syntax: Math.exp( value ) , where value is the value for which you want e to the power.
floor	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the greatest integer less than or equal to the value you pass.
	Syntax: Math.floor( value ) , where value is the value you want to round down.
log	x	x	x	x	x	x	x	x	x	x
	Returns: number
	Returns the natural log, base e, of a value.
	Syntax: Math.log( value ) , where value is the value for which you want the natural log.
max	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the greater of the two values you pass to it.
	Syntax: Math.max( value1 , value2 ) , where value1 and value2 are the values you're comparing.
min	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the lesser of the two values you pass to it.
	Syntax: Math.min( value1 , value2 ) , where value1 and value2 are the values you're comparing.
pow	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the value of a base expression raised to a given power.
	Syntax: Math.pow( base , exponent ) .
random	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns a random number between 0 and 1.
	Syntax: Math.random() .
round	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns an numeric expression rounded to the nearest integer.
	Math.round( value ) . If the decimal part of value is 0.5 or greater, the return value is the smallest integer that is still greater than value . Otherwise, the return value is the largest integer less than or equal to value .
sin	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the sine of a value.
	Syntax: Math.sin( value ) , where value is the value, in radians, for which you want the sine.
sqrt	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the square root of a value.
	Syntax: Math.sqrt( value ) , where value is the value, in radians, for which you want the square root.
tan	x	x	x	x	x	x	x	x	x	x
	Returns: Number
	Returns the tangent of a value.
	Syntax: Math.tan( value ) , where value is the value, in radians, for which you want the tangent.