| Previous Contents Index Next |
| Core JavaScript Reference 1.5 |
A built-in object that has properties and methods for mathematical constants and functions. For example, the Math object's PI property has the value of pi.
Created by
The Math object is a top-level, predefined JavaScript object. You can automatically access it without using a constructor or calling a method.
Description
All properties and methods of Math are static. You refer to the constant PI as Math.PI and you call the sine function as Math.sin(x), where x is the method's argument. Constants are defined with the full precision of real numbers in JavaScript.It is often convenient to use the with statement when a section of code uses several Math constants and methods, so you don't have to type "Math" repeatedly. For example,
with (Math) {
a = PI * r*r
y = r*sin(theta)
x = r*cos(theta)
}
Property
Description
E
Euler's constant and the base of natural logarithms, approximately 2.718.
LN2
LN10
LOG2E
LOG10E
PI
Ratio of the circumference of a circle to its diameter, approximately 3.14159.
SQRT1_2
Square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707.
SQRT2
Method
Description
abs
acos
asin
atan
atan2
ceil
Returns the smallest integer greater than or equal to a number.
cos
exp
Returns Enumber, where number is the argument, and E is Euler's constant, the base of the natural logarithms.
floor
log
max
min
pow
random
round
Returns the value of a number rounded to the nearest integer.
sin
sqrt
tan
In addition, this object inherits the watch and unwatch methods from Object.
Returns the absolute value of a number.
x
Examples
The following function returns the absolute value of the variable x:function getAbs(x) {
return Math.abs(x)
}
Description
Because abs is a static method of Math, you always use it as Math.abs(), rather than as a method of a Math object you created.
Returns the arccosine (in radians) of a number.
x
Description
The acos method returns a numeric value between 0 and pi radians. If the value of number is outside this range, it returns NaN.Because acos is a static method of Math, you always use it as Math.acos(), rather than as a method of a Math object you created.
Examples
The following function returns the arccosine of the variable x:function getAcos(x) {
return Math.acos(x)
}If you pass -1 to getAcos, it returns 3.141592653589793; if you pass 2, it returns NaN because 2 is out of range.
See also
Math.asin, Math.atan, Math.atan2, Math.cos, Math.sin, Math.tan
Returns the arcsine (in radians) of a number.
x
Description
The asin method returns a numeric value between -pi/2 and pi/2 radians. If the value of number is outside this range, it returns NaN.Because asin is a static method of Math, you always use it as Math.asin(), rather than as a method of a Math object you created.
Examples
The following function returns the arcsine of the variable x:function getAsin(x) {
return Math.asin(x)
}If you pass getAsin the value 1, it returns 1.570796326794897 (pi/2); if you pass it the value 2, it returns NaN because 2 is out of range.
See also
Math.acos, Math.atan, Math.atan2, Math.cos, Math.sin, Math.tan
Returns the arctangent (in radians) of a number.
x
Description
The atan method returns a numeric value between -pi/2 and pi/2 radians.Because atan is a static method of Math, you always use it as Math.atan(), rather than as a method of a Math object you created.
Examples
The following function returns the arctangent of the variable x:function getAtan(x) {
return Math.atan(x)
}If you pass getAtan the value 1, it returns 0.7853981633974483; if you pass it the value .5, it returns 0.4636476090008061.
See also
Math.acos, Math.asin, Math.atan2, Math.cos, Math.sin, Math.tan
Returns the arctangent of the quotient of its arguments.
y, x
Description
The atan2 method returns a numeric value between -pi and pi representing the angle theta of an (x,y) point. This is the counterclockwise angle, measured in radians, between the positive X axis, and the point (x,y). Note that the arguments to this function pass the y-coordinate first and the x-coordinate second.atan2 is passed separate x and y arguments, and atan is passed the ratio of those two arguments.
Because atan2 is a static method of Math, you always use it as Math.atan2(), rather than as a method of a Math object you created.
Examples
The following function returns the angle of the polar coordinate:function getAtan2(x,y) {
return Math.atan2(x,y)
}If you pass getAtan2 the values (90,15), it returns 1.4056476493802699; if you pass it the values (15,90), it returns 0.16514867741462683.
See also
Math.acos, Math.asin, Math.atan, Math.cos, Math.sin, Math.tan
Returns the smallest integer greater than or equal to a number.
x
Description
Because ceil is a static method of Math, you always use it as Math.ceil(), rather than as a method of a Math object you created.
Examples
The following function returns the ceil value of the variable x:function getCeil(x) {
return Math.ceil(x)
}If you pass 45.95 to getCeil, it returns 46; if you pass -45.95, it returns -45.
See also
Math.floor
Returns the cosine of a number.
x
Description
The cos method returns a numeric value between -1 and 1, which represents the cosine of the angle.Because cos is a static method of Math, you always use it as Math.cos(), rather than as a method of a Math object you created.
Examples
The following function returns the cosine of the variable x:function getCos(x) {
return Math.cos(x)
}If x equals 2*Math.PI, getCos returns 1; if x equals Math.PI, the getCos method returns -1.
See also
Math.acos, Math.asin, Math.atan, Math.atan2, Math.sin, Math.tan
Euler's constant and the base of natural logarithms, approximately 2.718.
Description
Because E is a static property of Math, you always use it as Math.E, rather than as a property of a Math object you created.
Examples
The following function returns Euler's constant:function getEuler() {
return Math.E
}
Returns Ex, where x is the argument, and E is Euler's constant, the base of the natural logarithms.
x
Description
Because exp is a static method of Math, you always use it as Math.exp(), rather than as a method of a Math object you created.
Examples
The following function returns the exponential value of the variable x:function getExp(x) {
return Math.exp(x)
}If you pass getExp the value 1, it returns 2.718281828459045.
See also
Math.E, Math.log, Math.pow
Returns the largest integer less than or equal to a number.
x
Description
Because floor is a static method of Math, you always use it as Math.floor(), rather than as a method of a Math object you created.
Examples
The following function returns the floor value of the variable x:function getFloor(x) {
return Math.floor(x)
}If you pass 45.95 to getFloor, it returns 45; if you pass -45.95, it returns -46.
See also
Math.ceil
The natural logarithm of 2, approximately 0.693.
Examples
The following function returns the natural log of 2:function getNatLog2() {
return Math.LN2
}
Description
Because LN2 is a static property of Math, you always use it as Math.LN2, rather than as a property of a Math object you created.
The natural logarithm of 10, approximately 2.302.
Examples
The following function returns the natural log of 10:function getNatLog10() {
return Math.LN10
}
Description
Because LN10 is a static property of Math, you always use it as Math.LN10, rather than as a property of a Math object you created.
Returns the natural logarithm (base E) of a number.
x
Description
If the value of number is negative, the return value is always NaN.Because log is a static method of Math, you always use it as Math.log(), rather than as a method of a Math object you created.
Examples
The following function returns the natural log of the variable x:function getLog(x) {
return Math.log(x)
}If you pass getLog the value 10, it returns 2.302585092994046; if you pass it the value 0, it returns -Infinity; if you pass it the value -1, it returns NaN because -1 is out of range.
The base 2 logarithm of E (approximately 1.442).
Examples
The following function returns the base 2 logarithm of E:function getLog2e() {
return Math.LOG2E
}
Description
Because LOG2E is a static property of Math, you always use it as Math.LOG2E, rather than as a property of a Math object you created.
The base 10 logarithm of E (approximately 0.434).
Examples
The following function returns the base 10 logarithm of E:function getLog10e() {
return Math.LOG10E
}
Description
Because LOG10E is a static property of Math, you always use it as Math.LOG10E, rather than as a property of a Math object you created.
Returns the larger of two numbers.
x, y
Description
Because max is a static method of Math, you always use it as Math.max(), rather than as a method of a Math object you created.
Examples
The following function evaluates the variables x and y:function getMax(x,y) {
return Math.max(x,y)
}If you pass getMax the values 10 and 20, it returns 20; if you pass it the values -10 and -20, it returns -10.
See also
Math.min
Returns the smaller of two numbers.
x, y
Description
Because min is a static method of Math, you always use it as Math.min(), rather than as a method of a Math object you created.
Examples
The following function evaluates the variables x and y:function getMin(x,y) {
return Math.min(x,y)
}If you pass getMin the values 10 and 20, it returns 10; if you pass it the values -10 and -20, it returns -20.
See also
Math.max
The ratio of the circumference of a circle to its diameter, approximately 3.14159.
Examples
The following function returns the value of pi:function getPi() {
return Math.PI
}
Description
Because PI is a static property of Math, you always use it as Math.PI, rather than as a property of a Math object you created.
Returns base to the exponent power, that is, baseexponent.
base
exponent
Description
Because pow is a static method of Math, you always use it as Math.pow(), rather than as a method of a Math object you created.
Examples
function raisePower(x,y) {
return Math.pow(x,y)
}If x is 7 and y is 2, raisePower returns 49 (7 to the power of 2).
Returns a pseudo-random number between 0 and 1. The random number generator is seeded from the current time, as in Java.
Description
Because random is a static method of Math, you always use it as Math.random(), rather than as a method of a Math object you created.
Examples
//Returns a random number between 0 and 1
function getRandom() {
return Math.random()
}
Returns the value of a number rounded to the nearest integer.
x
Description
If the fractional portion of number is .5 or greater, the argument is rounded to the next higher integer. If the fractional portion of number is less than .5, the argument is rounded to the next lower integer.Because round is a static method of Math, you always use it as Math.round(), rather than as a method of a Math object you created.
Examples
//Returns the value 20
x=Math.round(20.49)//Returns the value 21
x=Math.round(20.5)//Returns the value -20
x=Math.round(-20.5)//Returns the value -21
x=Math.round(-20.51)
x
Description
The sin method returns a numeric value between -1 and 1, which represents the sine of the argument.Because sin is a static method of Math, you always use it as Math.sin(), rather than as a method of a Math object you created.
Examples
The following function returns the sine of the variable x:function getSine(x) {
return Math.sin(x)
}If you pass getSine the value Math.PI/2, it returns 1.
See also
Math.acos, Math.asin, Math.atan, Math.atan2, Math.cos, Math.tan
Returns the square root of a number.
x
Description
If the value of number is negative, sqrt returns NaN.Because sqrt is a static method of Math, you always use it as Math.sqrt(), rather than as a method of a Math object you created.
Examples
The following function returns the square root of the variable x:function getRoot(x) {
return Math.sqrt(x)
}If you pass getRoot the value 9, it returns 3; if you pass it the value 2, it returns 1.414213562373095.
The square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707.
Examples
The following function returns 1 over the square root of 2:function getRoot1_2() {
return Math.SQRT1_2
}
Description
Because SQRT1_2 is a static property of Math, you always use it as Math.SQRT1_2, rather than as a property of a Math object you created.
The square root of 2, approximately 1.414.
Examples
The following function returns the square root of 2:function getRoot2() {
return Math.SQRT2
}
Description
Because SQRT2 is a static property of Math, you always use it as Math.SQRT2, rather than as a property of a Math object you created.
Returns the tangent of a number.
x
Description
The tan method returns a numeric value that represents the tangent of the angle.Because tan is a static method of Math, you always use it as Math.tan(), rather than as a method of a Math object you created.
Examples
The following function returns the tangent of the variable x:function getTan(x) {
return Math.tan(x)
}
See also
Math.acos, Math.asin, Math.atan, Math.atan2, Math.cos, Math.sin
Previous Contents Index Next
Copyright © 2000 Netscape Communications Corp. All rights reserved.
Last Updated September 28, 2000