jQuery set checkbox checked

you have to use the 'prop' function :

.prop('checked', true);

Before jQuery 1.6 (see user2063626's answer):

.attr('checked','checked')

Taking all of the proposed answers and applying them to my situation - trying to check or uncheck a checkbox based on a retrieved value of true (should check the box) or false (should not check the box) - I tried all of the above and found that using .prop("checked", true) and .prop("checked", false) were the correct solution.

I can't add comments or up answers yet, but I felt this was important enough to add to the conversation.

Here is the longhand code for a fullcalendar modification that says if the retrieved value "allDay" is true, then check the checkbox with ID "even_allday_yn":

if (allDay)
{
    $( "#even_allday_yn").prop('checked', true);
}
else
{
    $( "#even_allday_yn").prop('checked', false);
}

Try below code :

$("div.row-form input[type='checkbox']").attr('checked','checked')

OR

$("div.row-form #estado_cat").attr("checked","checked");

OR

$("div.row-form #estado_cat").attr("checked",true);

"checked" attribute 'ticks' the checkbox as soon as it exists. So to check/uncheck a checkbox you have to set/unset the attribute.

For checking the box:

$('#myCheckbox').attr('checked', 'checked');

For unchecking the box:

$('#myCheckbox').removeAttr('checked');

For testing the checked status:

if ($('#myCheckbox').is(':checked'))

Hope it helps...

Since you are in a modal window (whether dynamic or in the page) you can use the following code to accomplish your goal: (I ran into the same problem on my site and this is how I fixed it)

HTML:

<div class="content-container" style="text-align: right;">
    <input type="checkbox" id="QueryGroupCopyQueries">
    <label for="QueryGroupCopyQueries">Create Copies</label>                                                   
</div>

CODE:

$.each(queriesToAddToGroup, function (index, query) {
    if (query.groupAddType === queriesGroupAddType.COPY) {

        // USE FIND against your dynamic window and PROP to set the value
        // if you are using JQUERY 1.6 or higher.
        $(kendoWindow).find("input#QueryGroupCopyQueries").prop("checked", true);

        return;
    }

In the above "kendoWindow" is my window (mine is dynamic, but I also do this when appending to an element directly in the page). I am looping through an array of data ("queriesToAddToGroup") to see if any rows have an attribute of COPY. If so I want to turn on the checkbox within the window that sets that attribute when a user saves from this window.