f IsCallable(<var>adder</var>) is <emu-val>false</emu-val>, throw a TypeError.</li></ol></li><li>Let <var>entries</var> be the List that is <var>map</var>.<var class="field">[[MapData]]</var></li><li>Let <var>newMapData</var> be new empty List.</li><li>For each Record { <var class="field">[[Key]]</var>, <var class="field">[[Value]]</var>&nbsp;} <var>p</var> that is an element of entries, do<ol><li>If <var>p</var>.<var class="field">[[Key]]</var> is not empty, then<ol><li>Let <var>key</var> be <var>p</var>.<