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I add an element to an array when the checkbox is checked and I need to remove it when it is unchecked. I use splice to remove an element. I just can't seem to call an event when it's unchecked. I tried using this:

if ($('input[name="'+category+'"]:checked'))
    item_id[category] = $(this).attr("id");
else 
    item_id.splice(category, 1);

It adds the needed element ok, when the checkbox is checked, but it doesn't seem to remove it when it's unchecked. Variable category is a loop variable and is correct.

If someone can work this out, it would be greatly appreciated.

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  • Is item_id definitely an array, and is category definitely an integer? Commented Nov 23, 2010 at 10:02

4 Answers 4

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2

jQuery selectors always return an object whether an element is matched or not.

What you've effectively got is:

if (new Object())
    item_id[category] = $(this).attr("id");
else 
    item_id.splice(category, 1);

Objects are always truthy (no matter if it's an empty object, or an object John Resig initialized), so this if statement will never execute the else.

What you're probably after is:

if ($('input[name="'+category+'"]:checked').length)
    item_id[category] = $(this).attr("id");
else 
    item_id.splice(category, 1);

Which checks the length property instead.

This still won't work however, as splice() will shift all elements in your array; making the category wrong.

If your binding the event on a number of checkbox elements, it will be unwise to use .bind() (and it's counterparts .click()), as this method will bind an event for each checkbox. Instead, use .live(), or .delegate(); this will bind one event to an ancestor of all checkbox elements, and listen for event (using JavaScripts event bubbling), which is much more efficient.

Taking both of these points into consideration, you might fancy something like this.

$(yourJquerySelector).live('change', function () {
    var category = '?' // (this.value ?)

    item_id[category] = this.checked ? this.id : undefined;
});
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5 Comments

Thanks a lot for your input. Now what I effectively have is this: i check for checked checkbox length, and it will add the element to an array, but it won't ever call else (I checked with an alert). When it's checked, it's length is 1, but when it's not, it won't return anything, hence, else isn't executed. It's the same with the .is() method. I use .live() with 'change' event.
@donkapone: What do you mean "it won't return anything"? If no elements are matched, the length will be 0. This sort of thing appears in jQuery code many hundreds of times. Can you update your question to include exactly what you've got now? (and maybe a little bit extra; such as the whole event binding and variable declarations of item_id and category).
I'd have to copy the whole code which is about 200 lines for you to understand where item_id and category are declared, because they're all over the place. What I meant by saying it won't return anything is that I printed out the length into Firebug Console, and it shows 1, when it's selected and it won't print out anything when it's not selected. Here's the code: pastebin.com/8CGLtqm7 The pasted code is in the updateDivResult() method, the events are called at the end, when the body is loaded. item_id gets its value from getDefault() method. products_custom is an array of my values.
@donkapone: If it's not printing out anything, it isn't getting run. Try alerting a string (alert("This gets called!")). If you're trying to decide whether the checkbox that was changed is ticked in if ($('input[name="'+category+'"]:checked').length), just change it to if (this.checked). Its much, much, much more efficient, plus the jQuery version does more than just return whether that checkbox is checked; it checks whether any element whose name is the value of the variable category is checked. Aslong as at-least one of them is, it will return true.
@donkapone: Also, something to consider once this problem gets resolved, it's not recommended to use for (.. in ..) for iterating over array elements; for .. in should be used to loop through object members. Stick to for (var ..;.. < ..; ..++) for iterating through array elements.
1

Not entirely sure what you are after to be honest, but here is my solution to this,hope it works for you in some way

Javascript Array - indexOf Method: http://www.tutorialspoint.com/javascript/array_indexof.htm

<script>

if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt /*, from*/)
  {
    var len = this.length;

    var from = Number(arguments[1]) || 0;
    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);
    if (from < 0)
      from += len;

    for (; from < len; from++)
    {
      if (from in this &&
          this[from] === elt)
        return from;
    }
    return -1;
  };
}

$(function() {

    var checkedItems = new Array();

    $(":checkbox").change(function () {
        if($(this).attr('checked'))
        {
        checkedItems.push($(this).attr("id"));
         }
        else
        {
        var index = checkedItems.indexOf($(this).attr("id"));
        checkedItems.splice(index,1);
        }
    });

});
</script>

HTML

<input type="checkbox" id="c1" value="1">
<input type="checkbox" id="c2" value="2">
<input type="checkbox" id="c3" value="3">
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2 Comments

this works like I asked. There's just some other problems still to solve. Thank you.
oh really there are some problems ? is it with the code i posted or sumthing i forgot to include in the code?
1

The splice function is meant to return what's removed, so start debugging by displaying its return value.

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Comments

1

Change your if condition to:

$('input[name="'+category+'"]').is(':checked')

As mentioned by Matt, your current if condition is a selector that returns a list of jQuery elements. Testing the number of elements returned (using the length property) would also do the trick.

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