Document: firstElementChild property
目录
The Document.firstElementChild read-only property
returns the document's first child Element, or null if there
are no child elements.
For HTML documents, this is usually the only child, the root <html> element.
See Element.firstElementChild for the first child element of specific elements within a document.
Value
An Element object, or null.
Examples
document.firstElementChild;
// returns the root <html> element, the only child of the document