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Why do I get undefined when trying to get a dynamically added data attribute?

March 4, 2024

I’m trying to get the value for data-tab-id based on the class .tab-btn.active | however, the result keeps returning undefined.

This is where I add the data attribute

$navigation.find(".tab-btn").each(function(i, ele) {
        $(ele).attr("data-tab-id", i);
    });

This is where I retrieve it

var autoSwitch = setInterval(function() {

    //Get maximum # of tabs
    maxTabs = $(".tab-btn").length;
                        
    //Get the currently active button
    pastActiveBtn = $(".tab-btn").find(".active");
    pastId = pastActiveBtn.data('tabId'); //I have also tried tab-id; also 'undefined'

    console.log(pastId); //OUTPUT = undefined

});

If anyone knows why I am getting this, I’d appreciate it.

>Solution :

Try using
pastActiveBtn = $(".tab-btn").filter(".active");
Filter will look at the currently matched element, while find will look at the descendants.
More details about the difference between filter and find in this answer.