have a <emu-const><var class="field">[[MapData]]</var></emu-const> internal slot, throw a <emu-val>TypeError</emu-val> exception.</li></ol></li><li>If IsCallable(<var>callbackfn</var>) is false, throw a <emu-val>TypeError</emu-val> exception.</li><li>If <var>thisArg</var> was supplied, let <var>T</var> be <var>thisArg</var>; else let <var>T</var> be <emu-val>undefined</emu-val>.</li><li>Let <var>entries</var> be the List that is <var>map</var>.<var class="field">[[MapData]]</var>.</li><li>For each Record { 