tion</span> <span class="variable">errorHandler</span>(<span class="variable">err</span>, <span class="variable">req</span>, <span class="variable">res</span>, <span class="variable">next</span>) {
    <span class="variable">res</span>.<span class="variable">writeHead</span>(<span class="number integer">500</span>, { <span class="string">'Content-Type'</span>: <span class="string">'text/plain'</span> });
    <span class="variable">res</span>.<span class="variable">end</span>(<span class="variable">err</span