Question

I experience a very weird JavaScript behavior.
I’m using jQuery 1.9 and farbtastic color picker:

While this code works:

$('#colorpicker_1').hide();
$('#colorpicker_1').farbtastic('#color_1');
$('#colorbody_1').click(function(){$('#colorpicker_1').slideToggle()});

$('#colorpicker_2').hide();
$('#colorpicker_2').farbtastic('#color_2');
$('#colorbody_2').click(function(){$('#colorpicker_2').slideToggle()});

$('#colorpicker_3').hide();
$('#colorpicker_3').farbtastic('#color_3');
$('#colorbody_3').click(function(){$('#colorpicker_3').slideToggle()});

$('#colorpicker_4').hide();
$('#colorpicker_4').farbtastic('#color_4');
$('#colorbody_4').click(function(){$('#colorpicker_4').slideToggle()});

this does not work, and i have absolutely no clue, why it does not:

var cstatusIDs = new Array();
cstatusIDs.push(1);
cstatusIDs.push(2);
cstatusIDs.push(3);
cstatusIDs.push(4);

for(var z=0; z < cstatusIDs.length; z++)
{
    var cstatus_id = cstatusIDs[z];

    console.log(cstatus_id); // outputs 1,2,3,4

    $('#colorpicker_'+cstatus_id).hide();
    $('#colorpicker_'+cstatus_id).farbtastic('#color_'+cstatus_id);
    $('#colorbody_'+cstatus_id).click(function(){$('#colorpicker_'+cstatus_id).slideToggle()});
}

Any ideas?

Answer 1

The problem is the fact that cstatus_id is defined outside the scope of your click handler, and its value changes each time the loop runs. Since the click handler is not actually evaluated until you trigger a click event, at that time all of the handlers use the last value of cstatus_id.

To work around this, wrap the handler in a closure so that each instance gets its own unique id.

var cstatusIDs = [1, 2, 3, 4];

for(var z=0; z < cstatusIDs.length; z++)
{
    var cstatus_id = cstatusIDs[z];

    console.log(cstatus_id); // outputs 1,2,3,4

    $('#colorpicker_'+cstatus_id).hide();
    $('#colorpicker_'+cstatus_id).farbtastic('#color_'+cstatus_id);

    (function(id) {
        $('#colorbody_' + id).click( function() {
            $('#colorpicker_' + id).slideToggle()
        });
    })(cstatus_id)
}