2010年11月7日星期日

JavaScript random()方法

Definition and Usage
定义与用法

The random() method returns a random number between 0 and 1.
random() 方法能返回0到1之间的一个随机数
Syntax
语法

Math.random()



Example
举例

In this example we will get a random number between 0 and 1:
在这个举例中我们将得到一个在0到1之间的随机数:
<script type="text/javascript">
document.write(Math.random())
</script>


The output of the code above can be:
输出结果为:0.6088752210444985


Generating a random number in JavaScript

A popular question on CodingForums.com is how to generate a random number in JavaScript. A random number is useful- if not required- in the creation of certain popular JS applications, such as a dice, random image script, or random link generator. In this JavaScript article, we'll learn how to output a random number that falls within the range 1 to x, where x is any integer >1.

The results may be unpredictable, but the technique to getting them certainly is not. To generate a random number in JavaScript, simply use the following code:

var randomnumber=Math.floor(Math.random()*11)

where 11 dictates that the random number will fall between 0-10. To increase the range to, say, 100, simply change 11 to 101 instead.

Some of you may be curious as to why Math.floor(), instead of Math.round(), is used in the above code. While both successfully round off its containing parameter to an integer within the designated range, Math.floor does so more "evenly", so the resulting integer isn't lopsided towards either end of the number spectrum. In other words, a more random number is returned using Math.floor(). By the way, the Random Motivational script uses just the aforementioned code to randomly display a quote.

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