Generate Random Numbers Within a Range using JavaScript

A formula for generating a random number within a given range using JavaScript is as follows:

Math.floor(Math.random() * (UpperRange - LowerRange + 1)) + LowerRange;

So to generate a random number between 25 and 75, the equation would be

Math.floor(Math.random() * (75-25+1)) + 25;

i.e.

Math.floor(Math.random() * 51) + 25;

Here’s the entire code:

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>Random Number in JavaScript</title>
    <script type="text/javascript">
        var randomNumber = Math.floor(Math.random() * 51) + 25;
        document.write("<p>" + randomNumber + "</p>");      
    </script>
</head>
<body>
</body>
</html>

See a Live Demo

About The Author

Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.

2 comments:

Anonymous said...: Thanks! What if I want it to be equal than or greater to X, but less than Y?

benjamin.morse.archer@gmail.com; March 2, 2011 at 6:12 PM
Suprotim Agarwal said...: Ben: In that case use the following:

Math.floor(Math.random()*(Y-X)) + X;

Although I have not tested it, but it should work!; March 2, 2011 at 9:18 PM