You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="lang_core|30" />
  </query-continue>
  <query>
    <pages>
      <page pageid="4" ns="0" title="node.js" />
      <page pageid="12" ns="0" title="Express" />
      <page pageid="14" ns="0" title="Expressをインストールする" />
      <page pageid="15" ns="0" title="ExpressによるHello World" />
      <page pageid="19" ns="0" title="node.jsでハッシュを計算する" />
      <page pageid="27" ns="0" title="JavaScript言語解説" />
      <page pageid="29" ns="0" title="コメント" />
      <page pageid="61" ns="0" title="JSDoc" />
      <page pageid="63" ns="0" title="jsdoc.vim" />
    </pages>
  </query>
</api>