How do I empty an input value with jQuery?

I’m trying to make a modal dialog with images where you can select multiple images. I need to get values from an input and then to empty it, but I cannot empty the input. I tried `.val('')` and `.val(null)`, but neither worked for me. Here is the full code: ``` $("#hdselect").click(function(){ $(".modal").html(""); $.post('mediaservice.php',{hd:'ok',images:$("#hdimages").val()},function(data){ $(".modal").append(data); }); $(".modal").dialog({ 'modal':true, 'title':"Click the image to select", 'width':960, 'height':600, 'resizable':false, 'show': {effect: 'drop', direction: "up"}, 'buttons': {"Ok": function() { var hd=Array(); var hdval=$("#hdimages").val(); $("#hdimages").attr('value',' '); $("input[name='hd[]']:checked").each(function(){ hd.push($(this).val()); }); if(hdval!=''){ hdval=hdval+","+hd; }else{ hdval=hd; } $("#hdimages").val(hdval); var images=$("#hdimages").val(); $.post('mediaservice.php',{getHd:images},function(data){ $("#imgthumbBase").append(data); }); $(this).dialog("close"); } } }); }); ``` The idea is that the user clicks a button and a modal dialog opens with multiple images and checkboxes. At this point I need to get the values from an input, and then clear it.