Question: What is the equivalent of jQuery's 

**closest()** function in prototypeJS?

and **html()** function in prototypeJS?

Answer: 
I think the .html() function looks like this in prototype

To retrieve the html

```
$('fruits').innerHTML;
// -> '<ul id="favorite"><li>kiwi</li><li>banana</li><li>apple</li></ul>'

```

To change the html

```
$('fruits').update('kiwi, banana and apple');
// -> HTMLElement

```

<http://www.prototypejs.org/api/element/update>
You might want to read [`getOffsetParent`](http://www.prototypejs.org/api/element/getOffsetParent) for `closest()` and [`update`](http://www.prototypejs.org/api/element/update) for `html()`