Can someone show me an example with "htmlcollection" please

With this code to be more specific, thanks.

var arr = Array.prototype.slice.call( htmlCollection )

Hello!

You could have something like this:

<form id="one">

</form>

<form id="two">

</form>

On your JavaScript:

console.log(Array.prototype.slice.call(document.forms))

So if I wanted I could use documenent.getElementById"one". Rather than document.forms?

What exactly are you trying to accomplish? You can use many different methods to acquire any comination of HTML elements, but you have given us no context.