/// Returns the node's first child in the tree, or `None` if the node is childless.
///
/// [(JavaScript docs)](https://developer.mozilla.org/en/docs/Web/API/Node/firstChild)
// https://dom.spec.whatwg.org/#ref-for-dom-node-firstchild
Returns the node's first child in the tree, or `None` if the node is childless.
Returns the node ' s first child in the tree or ` None ` if the node is childless .
fn first_child( &self ) -> Option< Node > {
        js!(
            return @{self.as_ref()}.firstChild;
        ).try_into().ok()
    }
fn first_child ( & self ) -> Option < Node > { js ! ( return { self as_ref ( ) } firstChild ) . try_into ( ) . ok ( ) }
Returns the node's first child in the tree, or `None` if the node is childless.
Returns the node ' s first child in the tree or ` None ` if the node is childless .
&self