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 JavaScript Random Number Generator
2003-05-27 16:47:35
Category: javascript:general
Description: Generate random numbers, round them to the nearest integer and print them in a select list.
Author: detour
Viewed: 29785
Rating: (120 votes)


 
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<!-- random.js by detour@metalshell.com -->
 
<!-- Generate 100 random numbers, round and print them.  -->
 
<!-- http://www.metalshell.com/ -->
 
<html>
<head>
<title>JavaScript Random Number Generator.</title>
</head>
<body>
 
<script type="text/javascript">
// Generate 100 random numbers and insert them into listbox
function genNumbers(listbox) {
  var i, rannum;
 
  for(i = 0; i < 100; i++) {
    // Math.random() returns a decimal number between
    // 0 and 1.  You multiple the result by the range
    // of numbers you want.
 
    // This will generate 0-100.
    rannum = Math.random()*100;
 
    // This would generate 145-200
    // rannum = Math.random()*55 + 145;
 
    // rannum is now a decimal value, to turn it into
    // an integer use Math.round to round it to the nearest
    // integer.  Math.floor(rannum) to always round down and
    // Math.ceil(rannum) to round up.
    rannum = Math.round(rannum);
 
    // If options[i] hasn't been created yet, create it.
    if(listbox.options[i] == null) {
      listbox.options[i] = new Option( rannum, rannum, 0, 0 );
    } else {
      listbox.options[i].value = rannum;
      listbox.options[i].text = rannum;
    }
  }
}
</script>
 
<form>
  <select name="ranlist" size="20" style="width:200px">
  </select><br><br>
  <input type="button" value="Generate Numbers"
         onclick="genNumbers(this.form.ranlist)";>
</form>
 
 
</body>
</html>