如何正确添加JQuery focusin事件

I am working on Google Apps Script with JQuery. I want to make focusin event work.

    var kojiNameElem = $("#koji_"+koji_id).find(".kojiName");

    var kojiNameId = kojiNameElem .attr("id");
    console.log("kojiNameId="+kojiNameId);//kojiNameId=koji-name-1

    $(kojiNameElem).on("focusin", function(e) {
    console.log("focusin");
    $(e.target).removeClass("bg-danger");
  }, false);

    console.log("done");//done

It seems that the program is ok till I can get the element: var kojiNameId = kojiNameElem .attr("id");. and besides, it goes till the end properly: console.log("done");. So, I think the part I add the event has something wrong. Help me please.