I want that when the vertical scrolling on the page exceeds 100px, Alert message `hello` should be displayed. I tried doing but it didn't work.

JavaScript

```
function fixSearch(body) {
var a=body.scrollTop;
if(a>100)
{
    alert("Hello");
}
}

```

HTML

```
<body onscroll="fixSearch(this)">
---------------------------
---------------------------
---------------------------
</body>

```