s line-numbers"><code class="js language-js"><span class="token keyword">class</span> <span class="token class-name">Child</span> <span class="token punctuation">{</span>
  <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">parent</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>parent <span class="token operator">=</span>