how to enable firestore persistence through web?

Actually I'm New in FIRESTORE . I don't know how to enable persistence throught web. In firestore API they gave some steps, but still i didnt understand

      firebase.initializeApp(config);
    saveButton.addEventListener("click",function(){
    var config = { 
apiKey: "AIzaSyCuUm2LH0OEeojblAYHN52RFGogHEcnsDY",
        authDomain: "cloud-7aac4.firebaseapp.com",
        databaseURL: "https://cloud-7aac4.firebaseio.com",
        projectId: "cloud-7aac4",
        storageBucket: "cloud-7aac4.appspot.com",
        messagingSenderId: "605897634030",
        presistence:"true"};
      firebase.initializeApp(config);
    /*enable persistence*/
    firebase.firestore().enablePersistence()
      .then(function() {
    var db = firebase.firestore();
    var docRef = db.doc('samples/alovelace');
     docRef.set({
        first: 'Ada',
        last: 'Lovelace',
        born: 1815
    });
      })
      .catch(function(err) {
          if (err.code == 'failed-precondition') {
              // Multiple tabs open, persistence can only be enabled
              // in one tab at a a time.
              // ...
          } else if (err.code == 'unimplemented') {
              // The current browser does not support all of the
              // features required to enable persistence
              // ...
          }
      });

And also is there is any possible to enable persistence using nodejs sdk without web?

Please point me to some working samples.