code: function search (){
      var replaced = 0
      var scripts = document.querySelectorAll('script')
      var script
      for (var i = 0; i < scripts.length; i++) {
        script = scripts[i]
        if (!script.src) continue
        if (/\/slackin\.js(\?.*)?$/.test(script.src)) {
          // replace script with iframe
          replace(script)
  
          // we abort the search for subsequent
          // slackin.js executions to exhaust
          // the queue
          return true
        }
      }
    }
docs: search for a script tag pointing to slackin.js