关于:nth-child() 选择器
nth-child(2)的意思是当前元素的父元素的第二个子元素
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<i>好</i> //i:nth-child(1)
<i>好</i> //i:nth-child(2)
<span>哈</span> //span:nth-child(3)
<span>哈</span> //span:nth-child(4)
<span>哈</span> //span:nth-child(5)
<i>好</i> //i:nth-child(6)
<span>哈</span> //span:nth-child(7)
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