复制iA Writer的对焦模式

Question

除了文本区域中当前文本行/段落外，是否有任何方法可以使所有内容变暗？

SimpleMDE正在使用textarea

链接到codepen demo

javascript

new SimpleMDE({
        element: document.getElementById("writer"),
        status: false,
        toolbar: false,
    });

HTML

<div class="writingArea">
<textarea id="writer" class="textEditor"># This one is bare
You can also choose to hide the statusbar and/or toolbar for a simple and clean appearance. This one also checks for misspelled words as you type!</textarea>
</div>

我在互联网上找不到任何指南/操作方法，所以我不知道该怎么做。否则，我不会问一个省力的问题