e.keyCode || e.which

HTML

<form>
    <input type="text"  />
    <input type="submit" />
</form>

JavaScript

$(function () {
    $('body').keypress(function (e) {
        if (e !== 'undefined') {
            if ((e.keyCode || e.which) == 13) {
            		
                alert("");
                e.preventDefault();
            }
        }
    });
});