Define callback

You can define two callbacks. Their names are self-explanatory:

onOpen
onClose

import React from 'react';
import { toast } from 'material-react-toastify';

function Example(){

  const notify = () => {
    toast("Hello there", {
      onOpen: () => window.alert('Called when I open'),
      onClose: () => window.alert('Called when I close')
    });
  }

  return <button onClick={notify}>Notify</button>;
}

Tip

If you use a component, the callback will also have access to the component props

import React from 'react';
import { toast } from 'material-react-toastify';

function Msg({ uid }){
  return <span>{uid}</span>;
}

function Example(){

  const notify = () => {
    toast(<Msg uid={"this is a uid for real"} />, {
      onOpen: ({ uid }) => window.alert(uid),
      onClose: ({ uid }) => window.alert(uid)
    });
  }

  return <button onClick={notify}>Notify</button>;
}