`ionic plugin add cordova-plugin-facebook4 --variable APP_ID="123456789" --variable APP_NAME="myApplication"`

Facebook.login(['email']).then( (response) => {
  let facebookCredential = firebase.auth.FacebookAuthProvider
      .credential(response.authResponse.accessToken);
  var that = this;
  firebase.auth().signInWithCredential(facebookCredential)
      .then((success) => {
        that.nav.setRoot(HomePage);
      })
      .catch((error) => {
        console.log("Firebase failure: " + JSON.stringify(error));
      });

}).catch((error) => { console.log(error) });

//facebook functions


 getDetailsFacebook() {
    var that=this;
    Facebook.getLoginStatus().then((response)=> {
      if (response.status == 'connected') {
        Facebook.api('/' + response.authResponse.userID + '?fields=id,name,gender', []).then((response)=> {
          //alert(JSON.stringify(response));
         that.uid = response.id;
          that.name=response.name;
         that.photo = "http://graph.facebook.com/"+that.uid+"/picture?type=large";
          that.user=new User(that.uid,that.fireUid,that.name, that.photo);
          that.profileData.setProfileData(that.user); // to create class for that

          //that.profileData.setProfile(that.uid,that.name,that.photo);
          //console.log("id:"+this.uid+this.name+this.photo);
        }, (error)=> {
          alert(error);
        })
      }
      else {
        alert('Not Logged in');
      }
    })

logOutFacebook(){
    Facebook.logout().then((response)=>
    {
      this.navCtrl.push(LoginPage);
      alert(JSON.stringify(response));
    },(error)=>{
      alert(error);
    })
  }