How to trigger jQuery change event in code

196
votes

I have a change event that is working fine but I need to get it to recurse.

So I have a function that is triggered on change that will "change" other drop downs based on a class selector (notice "drop downS", there could be more than one). This proxy change does not trigger the function and so fails. How can I get it to work?

Code

$(document).ready(function () {
    var activeDropBox = null;

    $("select.drop-box").change(function () {
        var questionId = $(this).attr("questionId");
        var selectedAnswer = $(this).val();
        activeDropBox = this;

        alert(this.questionId);

        $.ajax(
        {
            type: "POST",
            url: answerChangedActionUrl,
            data: { questionId: questionId, selectedValue: selectedAnswer },
            success: function (data) {
                SetElementVisibility(data.ShowElement, questionId);
            }, error: function (XMLHttpRequest, textStatus, errorThrown) {
                alert('XMLHttpRequest:' + XMLHttpRequest.responseText);
                alert('textStatus:' + textStatus);
                alert('errorThrown:' + errorThrown);
            }
        });
    });

    function SetElementVisibility(visible, questionId) {
        // I would like each child to then trigger the change event...
        $(".childOf" + questionId)[visible ? 'show' : 'hide']('slow');
        
        // Suggested code
        //$(".childOf" + questionId + " select").trigger("change");

        if (!visible) {
            $(".childOf" + questionId + " select").attr('selectedIndex', 0);
        }
    }
}

The suggestions so far seem to work, but as the change event triggers an ajax post it now seems to fail here. I'm going to play around with it but that is something for another question I feel.

5
javascriptjqueryjquery-events
Provide some code so we can have a look – Alex Rashkov
How can we tell you how to get it to work, when you haven't shown us what it is? – user113716
I thought it was a simple concept and didn't feel code was required. The answers so far seem to have understood my explanation and so I am trying their solutions now. If I don't have any joy I'll post some code. My implementation is actually much more complex. – 4imble
Sorted it, was a problem with me changing the value after the ajax post. Thanks all for the help. The suggestions posted worked like a charm. – 4imble

5 Answers

437
votes

Use the trigger() method 

$(selector).trigger("change");
41
votes

for me $('#element').val('...').change() is the best way.

21
votes

The parameterless form of the change() method triggers a change event. You can write something like:

$(document).ready(function() {
    $("#yourInitialElementID").change(function() {
        // Do something here...
        $(".yourDropDownClass").change();
    });
});
11
votes
$(selector).change()

.change()

.trigger("change")

Longer slower alternative, better for abstraction.

.trigger("change")

$(selector).trigger("change")
9
votes

Use That : 

$(selector).trigger("change");

OR

$('#id').trigger("click");

OR

$('.class').trigger(event);

Trigger can be any event that javascript support.. Hope it's easy to understandable to all of You.