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Generating weighed random
numbers in JavaScript
While it's impossible to forecast the exact occurrence of a random event,
even a non-mathematician would agree we can manipulate the likelihood of
something occurring. For example, in the case of winning the lottery, that
would simply mean buying more tickets (and having your dreams dashed
multiple times of course). In this tutorial, we take a stab at generating
weighed random numbers, or random numbers with some more likely to show up
than others. This is useful in situations where you need a more refined
random engine, for example in a banner script that can display some
banners more often than others.
Lets begin by looking back. As discussed
in this tutorial, to generate a random number in JavaScript, the code:
var randomnumber=Math.floor(Math.random()*11)
will do nicely, whereby a random number between 0 to 10 is generated.
 Increasing the odds
When we talk about manipulating the chances of a particular number
popping up, first of all, it must be relative to some other numbers. This
may seem obvious, but important to establish nevertheless. Even in the
above example, there is an implied set of numbers, namely, 1 to 10, with
the odds of each one getting picked being equal. Putting a weight on a
number means changing this "equality."
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