obj.insertAdjacentElement(("where", elementObjectReference) 把elementObjectReference插入到obj的where 位置。where取值：BeforeBegin： Before start tag of current element, as a previous sibling AfterBegin: Immediately after current element's start tag, as a first child element BeforeEnd: Immediately before current element's end tag, as a last child element AfterEnd: After end tag of current element, as a next sibling
AfterBegin: Immediately after current element's start tag, as a first child element
BeforeEnd: Immediately before current element's end tag, as a last child element
AfterEnd: After end tag of current element, as a next sibling
obj.applyElement(elementObject[, type]) 给obj插入孩子elementObject
逻辑自己看吧。