authenticate() {
    fetch(this.state.authenticationURL, {
      headers: {
        "Content-Type": "application/json"
      },
      credentials: "include",
      method: "POST",
      body: JSON.stringify({
        username: this.state.username,
        password: this.state.password
      })
    })
      .then(response => {
        if (!response.ok) {
          response.json().then(error => {
            this.setState({
              showAlert: true,
              alertType: "danger",
              alertMessage: error.message
            });
          });
          Cookies.remove("userid");
          Cookies.remove("firstname");
          Cookies.remove("token");
        }
        return response.json();
      })
      .then(data => {
        this.setState({
          showAlert: true,
          alertType: "success",
          alertMessage: "Success!!"
        });
        Cookies.set("userid", data.userid);
        Cookies.set("firstname", data.firstname);
        Cookies.set("Token", data.token);
        window.location = this.state.redirectURL;
      })
      .catch(error => {
        console.error("Error cannot communicate with the API Server.");
      });
  }