title: How to access and make reactive the :class and :style changes in Vue component
body: <p>I have a Vue wrapper for Select2 component that I wrote a while ago. The wrapper is able to access the <code>bind:class</code> and <code>bind:style</code> attributes to pass along to the Select2 library, like so:</p>
  <pre><code>this.$vnode.data.staticClass // a string value of class=&quot;&quot; attribut
  this.$vnode.data.class       // an Object passed in via bind:class=&quot;{}&quot; attribute
  this.$vnode.data.style       // same as above but for style
  this.$vnode.data.staticStyle
  </code></pre>
  <p>Now I would really like to be able to detect changes to these, so that I could pass them along to Select2 innards.</p>
  <p>How can this be done?</p>