```
$(function() {

    var div  = $('div');

    $('input').click(function() {
        if($(this).is(':checked')) {
            div.html(div.text() += 49);    
        } else {
            div.html(div.text() -= 49);      
        }
    });

});

```

This is crazy, for some reason the `+=` and `-=` flag up bad assignment, why so?

By the way, I'm not using this code for anything, I know its bad, I'm just testing the `+=`

Example! <http://jsfiddle.net/dD73X/>