是否可以使用退格键防止跨度删除？
<div class="form-control" contenteditable="true">
<span class="correct-answer">
<span contenteditable="false">The correct answer is (A) 1 to 2. </span>
<span class="sentence" num="11">dgsdgsg. sgsdgs sgsgs.</span>
</span>
</div>示例：http://jsfiddle.net/pvj64px9/1/
The correct answer is (B) 2 to 3. and `Choice A (1 to 2) is incorrect. ` must not be deleted.
解决方法:
更新您的父容器以使contenteditable =“false”
<div id="window-kitkat" class="form-control" contenteditable="false">
并将您想要的可编辑元素设置为true,例如,
<span class="sentence" num="10" contenteditable="true">jfbgfdgdf sgdsgsd.</span>
