JavaScript学习与实践（23）

js中的Math，他用于完成一般的数学作业。

还是先给出几个例子，希望大家能够多加指正我的错误

1，怎么用round()

<html>
<body>
<script type="text/javascript">
document.write(Math.round(0.60) + "<br />")
document.write(Math.round(0.50) + "<br />")
document.write(Math.round(0.49) + "<br />")
document.write(Math.round(-4.40) + "<br />")
document.write(Math.round(-4.60))
</script>
</body>
</html>

大家可以去运行一下，结果是：

1
1
0
-4
-5

２怎么用random()来返回一个0和１之间的随机数

<html>
<body>
<script type="text/javascript">
document.write(Math.random())
</script>
</body>
</html>

大家自己去测试一下结果

３，大家用max()来返回比较数中的最大的数

<html>
<body>
<script type="text/javascript">
document.write(Math.max(5,7) + "<br />")
document.write(Math.max(-3,5) + "<br />")
document.write(Math.max(-3,-5) + "<br />")
document.write(Math.max(7.25,7.30))
</script>
</body>
</html>

结果是：

7
5
-3
7.3

４，大家用min()来返回比较数中最小的一个

<html>
<body>
<script type="text/javascript">
document.write(Math.min(5,7) + "<br />")
document.write(Math.min(-3,5) + "<br />")
document.write(Math.min(-3,-5) + "<br />")
document.write(Math.min(7.25,7.30))
</script>
</body>
</html>

结果是：

5
-3
-5
7.25

下面是这个对象中所有的方法和属性

Math Object Methods

FF: Firefox, N: Netscape, IE: Internet Explorer

Method	Description	FF	N	IE
abs(x)	Returns the absolute value of a number	1	2	3
acos(x)	Returns the arccosine of a number	1	2	3
asin(x)	Returns the arcsine of a number	1	2	3
atan(x)	Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians	1	2	3
atan2(y,x)	Returns the angle theta of an (x,y) point as a numeric value between -PI and PI radians	1	2	3
ceil(x)	Returns the value of a number rounded upwards to the nearest integer	1	2	3
cos(x)	Returns the cosine of a number	1	2	3
exp(x)	Returns the value of E^x	1	2	3
floor(x)	Returns the value of a number rounded downwards to the nearest integer	1	2	3
log(x)	Returns the natural logarithm (base E) of a number	1	2	3
max(x,y)	Returns the number with the highest value of x and y	1	2	3
min(x,y)	Returns the number with the lowest value of x and y	1	2	3
pow(x,y)	Returns the value of x to the power of y	1	2	3
random()	Returns a random number between 0 and 1	1	2	3
round(x)	Rounds a number to the nearest integer	1	2	3
sin(x)	Returns the sine of a number	1	2	3
sqrt(x)	Returns the square root of a number	1	2	3
tan(x)	Returns the tangent of an angle	1	2	3
toSource()	Represents the source code of an object	1	4	-
valueOf()	Returns the primitive value of a Math object	1	2	4

Math Object Properties

Property	Description	FF	N	IE
constructor	A reference to the function that created the object	1	2	4
E	Returns Euler's constant (approx. 2.718)	1	2	3
LN2	Returns the natural logarithm of 2 (approx. 0.693)	1	2	3
LN10	Returns the natural logarithm of 10 (approx. 2.302)	1	2	3
LOG2E	Returns the base-2 logarithm of E (approx. 1.414)	1	2	3
LOG10E	Returns the base-10 logarithm of E (approx. 0.434)	1	2	3
PI	Returns PI (approx. 3.14159)	1	2	3
prototype	Allows you to add properties and methods to the object	1	2	4
SQRT1_2	Returns the square root of 1/2 (approx. 0.707)	1	2	3
SQRT2	Returns the square root of 2 (approx. 1.414)	1	2	3

posted @ 2007-01-31 12:33 lxsohu 阅读(418) 评论(1) 收藏举报

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