Function that enables fields based on checkbox state I have simple code that just has to check if a checkbox is checked and if so enable some fields that, by default, should be disabled.

I have written the next code which I know can be severely improved. Could anyone tell me how? I tried getting the siblings of the checkbox also but that just caused some trouble.

$(function(){    
$('#amount').attr('disabled','disabled');
            $('#period').attr('disabled','disabled');
            $('#key').attr('disabled','disabled');
            $('#api').change(function(){
                if($('#apiEnabled').is(':checked')){
                    $('#amount').attr('disabled','');
                    $('#period').attr('disabled','');
                    $('#key').attr('disabled','');
                }else{
                    $('#amount').attr('disabled','disabled');
                    $('#period').attr('disabled','disabled');
                    $('#key').attr('disabled','disabled');
                }
            });
});
It's difficult to answer accurately without seeing your markup, but maybe you can use a multiple selector to alleviate code redundancy. You can also use prop() to enable or disable your elements more easily:

$(function() {
    var $elements = $("#amount, #period, #key");
    $elements.prop("disabled", true);
    $("#api").change(function() {
        $elements.prop("disabled", !$("#apiEnabled").is(":checked"));
    });
});