1">&#39;undefined&#39;</span><span class="p">)</span> <span class="o">&amp;&amp;</span>
            <span class="p">(</span><span class="k">typeof</span> <span class="k">this</span><span class="p">[</span><span class="nx">prop</span><span class="p">]</span> <span class="o">===</span> <span class="s1">&#39;undefined&#39;</span><span class="p">))</span> <span class="p">{</span>
            <span class="k">this</span><span class="p">.</span><span class="nx">set</span><span class="p">(</span><span class="nx">pr