Seen using form validator. Code that works:

$(document).ready(function(){

$("#tres").validate({

rules: {

contacto: {

required: true,

email: {

depends: function(element) {

return '''$("#treschk").is(':checked');'''

}

}

}

}

})

});

Code that doesn't work:

$(document).ready(function(){

$("#tres").validate({

rules: {

contacto: {

required: true,

email: {

depends: function(element) {

return $("#treschk:checked");

}

}

}

}

})

});

The test form:

<form id="tres">

<input type="checkbox" name="treschk" id="treschk"/>

<input type="text" id="contacto" name="contacto" class="required"/>

<input type="submit" value="Do!"/>

</form>