I'm trying to get the "quantity" attribute of multiple Elements ID at the same time.

Here's what I tried :

```
productMinimum : document.getElementsById("id1","id2").getAttribute("quantity")

```

How can I make this work? The "id1" and "id2" elements all have the "quantity" attribute.

Here's what it looks like from the HTML side :

```
<li class="product" name="RD-101" id="id1" price="18" quantity="2">
<li class="product" name="RD-101" id="id2" price="18" quantity="4"> 

```