title: Why use the `var` keyword in Vue.js?
body: <p>Every tutorial and code snippet I'm looking at while learning the framework all use <code>var</code> for their declarations, including <a href="https://v2.vuejs.org/v2/guide/index.html" rel="nofollow noreferrer">the official docs</a>.</p>
  <p>Preface, I'm just starting to learn Vue, so I know very little about it, but haven't found an answer yet.</p>
  <p>Same with other like assuming property name:</p>
  <pre><code>new Vue({
    data: data
  })
  </code></pre>
  <p>vs.</p>
  <pre><code>new Vue({
    data
  })
  </code></pre>
  <p>Am I wrong in assuming that ES6's <code>const</code> and <code>let</code> should be standard? Is there a reason to use <code>var</code> for Vue.js? Is there an issue with ES6?</p>