tabtracker.js

const tabs = require("sdk/tabs");
var optionsTab;
function OptionsPanel(){
    if(optionsTab == null){
        tabs.once("open", (tab) => {
          optionsTab = tab;
          optionsTab.once("close", () => {
            optionsTab = null;
          });
        });
        tabs.open( data.url("OptionsPanel.html") );
    }else{
        optionsTab.activate();
    }
}