n>);
    <span class="hljs-title function_">assert</span>(<span class="hljs-title function_">isCallable</span>(callbackFn), <span class="hljs-string">'callback is not a function'</span>);
    <span class="hljs-keyword">const</span> <span class="hljs-title class_">Ctor</span> = <span class="hljs-title class_">SpeciesConstructor</span>(<span class="hljs-variable language_">this</span>, <span class="hljs-title class_">Map</span>);
    <span class="hljs-keyword">const</span> retObj = <span class="hljs-keyword">