<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Car</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Vehicle</span> </span>{
<span class="hljs-function"><span class="hljs-title">constructor</span>(<span class="hljs-params">speed, cost</span>)</span> {
<span class="hljs-built_in">super</span>(speed);
<span class="hljs-keyword">var</span> c = <span class="hljs-built_in">Symbol</span>(<span class="hljs-string">'cost'</span>);
<span class="hljs-built_in">this</span>[c] = cost;
<span class="hljs-built_in">this</span>.intro = <span class="hljs-string">`This is a car runs at
<span class="hljs-subst">${speed}</span>.`</span>;
}
}
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