Javascript parentnode, parentelement, childnodes, children

Parentelement obtains the parent object in the object hierarchy.
Parentnode obtains the parent object in the document level.
Childnodes obtains the set of HTML elements and textnode objects that are directly descendant of a specified object.
Children obtains the set of DHTML objects that are directly descendant of objects.

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The parentnode and parentelement functions the same, while the childnodes and Children functions the same. However, parentnode and childnodes comply with W3C standards and are more common. The other two are only supported by IE. Firefox does not support the other two.

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That is to say, parentelement and children are the items of IE, which are not recognized elsewhere.
Their Standard Edition is parentnode and childnodes.
These two functions are the same as parentelement and children, and are standard and common.