getFileExtension from You Can't JavaScript Under Pressure

gistfile1.txt

//caution this is a very bad idea for a function even in javascript!

function getFileExtension(i) {
    
    // i will be a string, but it may not have a file extension.
    // return the file extension (with no period) if it has one, otherwise false
    
    var x;
    if(i.lastIndexOf(".") > -1) 
     x = i.substring(i.lastIndexOf(".")+1, i.length); 
    else 
     x = false;
    return x;
    
}