Core JavaScript 1.5 Reference:Global Objects:Math
From MDC
目录 |
[编辑] 摘要
核心对象
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.
[编辑] 创建
The Math object is a top-level, predefined JavaScript object. You can automatically access it without using a constructor or calling a method.
[编辑] 描述
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)
}
[编辑] 属性
E: Euler's constant and the base of natural logarithms, approximately 2.718.
LN2: Natural logarithm of 2, approximately 0.693.
LN10: Natural logarithm of 10, approximately 2.302.
LOG2E: Base 2 logarithm of E, approximately 1.442.
LOG10E: Base 10 logarithm of E, approximately 0.434.
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: Square root of 2, approximately 1.414.
[编辑] 方法
abs: 返回数字的绝对值。
acos: Returns the arccosine (in radians) of a number.
asin: Returns the arcsine (in radians) of a number.
atan: Returns the arctangent (in radians) of a number.
atan2: Returns the arctangent of the quotient of its arguments.
ceil: 返回大或者等于参数的最小整数（进一法取整）。
cos: Returns the cosine of a number.
exp: Returns Enumber, where number is the argument, and E is Euler's constant, the base of the natural logarithms.
floor: 返回小于或者等于参数的整数（去尾法取整）。
log: 返回以E为低的对数
max: 返回参数列表中的最大数
min: 返回参数列表中的最小数。
pow: Returns base to the exponent power, that is, base exponent.
random: 返回0-1之间的一个伪随机数。
round: Returns the value of a number rounded to the nearest integer.
sin: 返回正弦值 of a number.
sqrt: 返回平方根
tan: Returns the tangent of a number.