>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>If <var>set</var> does not have a <emu-const><var class="field">[[SetData]]</var></emu-const> internal slot, throw a <emu-val>TypeError</emu-val> exception.</li></ol></li><li>Let <var>elements</var> be CreateArrayFromList(items).</li><li>Let <var>adder</var> be ?&nbsp;Get(<var>set</var>, "add")</li><li>Return ?&nbsp;AddEntriesFromIterable(<var>set</var>, <var>elements</var>, <var>adder</var>).

</li></ol></emu-alg><p>The <code>length<