I'm trying to limit what our users will be able to type in inputs, using javascript/jquery.

Problem is, I have to limit this to Uppercase chars only, and numbers.

Here's what I coded previously :

                $(input).keydown(function(e){
                    if ($(input).attr("class")=="populationReference"){
                        var ValidPattern = /^[A-Z_0-9]*$/;
                        var char = String.fromCharCode(e.charCode);
                        if (!ValidPattern.test(char) && e.charCode!=0){
                            return false;
                            e.preventDefault();
                        }
                    }
                });

If Firefox supports charCode, IE doesn't. How then, could I test if the user is typing uppercase or lowercase characters ? Thanks for any help !