tion">observer</span><span class="token punctuation">(</span><span class="token string">'lastName'</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// The observer depends on lastName and so does fullName. Because observers</span>
    <span class="token comment">// are synchronous, when this function is called the v