How to identify the chosen selector in jQuery?

$('#select_id1, #select_id2, #select_id3').change(function() {
    // If '#select_id1' has changed, 'str' should be equal to 'sele开发者_JAVA百科ct_id1'.
    // If '#select_id2' has changed, 'str' should be equal to 'select_id2'.
    // If '#select_id3' has changed, 'str' should be equal to 'select_id3'.
    str = <what should be here ?>
});

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You can get the id of the element that invoked the change by this.id.

$('#select_id1, #select_id2, #select_id3').change(function() {
    str = this.id;
});

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Or (less efficiently):

$('#select_id1, #select_id2, #select_id3').change(function() {
  str = $(this).attr("id");
});

But basically this is set to the element on which the event took place.

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For the more general case, where not only IDs are used, as suggested by @Anurag, you can do the following:

// Save the selector
var selector = ".someClass, #someId, tr.someTrClass";

$(selector).change(function () {
    var selectors = selector.split(","),
        matching = []; // Remember that each element can
                       // match more than one selector
    for (var i = 0, s; s = selectors[i]; i++) {
        if ($(this).is(s)) matching.push(s);
    }

    str = matching.join(","); // Your list of all matching selectors
});

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You can either look at this.id directly or indirectly via a passed in event object:

$('#select_id1, #select_id2, #select_id3').change(function (e) {
    alert(e.target.id + ' == ' + this.id + ' ... ' + (e.target.id == this.id));
});

Most people just look at this but there are times when you might be interested in more than just the target of your event.