XML - get all values from tags into an array

I have what I am sure is a very straightforward question! I have an xml document and, using AJAX, I am wanting to get the values from tags with the same name into an array. XML:

<data>
  <instance>
    <term>Dog</term>
    <clicks>11235</clicks>
  </instance>
  <instance>
    <term>Cat</term>
    <clicks>6309</clicks>
  </instance>
</data>

My Javascript:

console.log(xml.getElementsByTagName("clicks")[0].childNodes[0].nodeValue); 

This only seems to return the first value. How do you return them all?