The TreeWalker.firstChild() method moves the current Node to the first visible child of the current node, and returns the found child. If no such child exists, it returns null and the current node is not changed.
firstChild()None.
A Node object or null.
const treeWalker = document.createTreeWalker(
document.body,
NodeFilter.SHOW_ELEMENT,
{
acceptNode(node) {
return NodeFilter.FILTER_ACCEPT;
},
},
false,
);
const node = treeWalker.firstChild(); // returns the first child of the root element, or null if noneTreeWalker interface it belongs to.