Ionic 2 - Page reloaded after post request

I'm trying to send data to server for saving. Everything works fine, but for some reason the page is reloaded right after the post request. This is the message I see in the console before the page is reloaded: "Dev server logger closed".

Here is the promise I use:

save(data){
    return new Promise((resolve) => {
      let headers = new Headers();
      headers.append('Content-Type', 'application/json');

      this.http.post('http://localhost:8080/api/postData', JSON.stringify(data), {headers: headers})
          .subscribe((res) => {
            resolve(res.json());
          });
    });
  }