l-1">).</span><span class="hl-7">reduce</span><span class="hl-1">((</span><span class="hl-0">doc</span><span class="hl-1">, </span><span class="hl-0">key</span><span class="hl-1">) </span><span class="hl-5">=&gt;</span><span class="hl-1"> </span><span class="hl-0">doc</span><span class="hl-1"> &amp;&amp; </span><span class="hl-0">doc</span><span class="hl-1">[</span><span class="hl-0">key</span><span class="hl-1">], </span><span class="hl-0">document</span><span class="hl-1">)</span><br/><span class="hl-1">