How can I create a function on the twitter, google, facebook share button?

Question

JavaScript

Good morning everyone, please help me out, the problem is: I need to add social network buttons to the site, and assign a callback function so that when a person clicks on the button to share a link, after clicking on the button, JS code should work for me, for example alert(" Thank you for sharing the link" ); It is the code that should work then, after the person has shared the link.
Vkontakte I was able to do, but the rest of the social. networking is very difficult to do because the documentation is in English. Facebook, Twitter, Google Plus.
Here is an example code in contact.

<div id="vk_like"></div>
<script type="text/javascript">
window.onload = function () {
 VK.init({apiId: 5144798, onlyWidgets: true});
 VK.Widgets.Like('vk_like', {type: 'button'}, 457);
 VK.Observer.subscribe("widgets.like.shared", function f(){ $("button").show('slow')}); Вот та самая строка когда срабатывает JavaScript.
}
</script>

Thank you very much in advance.