(Javascript) Crear un string alfanumérico random

<script type="text/javascript">
jQuery(document).ready(function($){ //set a random 9-char key
    var lenght = 9; // lenght of key
    var randomChars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz0123456789'; //any string
    var result = '';
    for ( var i = 0; i < lenght; i++ ) { //fills result with 9 random characters from randomChars
            result += randomChars.charAt(Math.floor(Math.random() * randomChars.length));
        }
    return result; // do anything with "result" string
});
</script>