tech-interview-handbook/utilities/javascript/treeEqual.js

function treeEqual(node1, node2) {
    if (!node1 && !node2) {
        return true;
    }
    if (!node1 || !node2) {
        return false;
    }
    return node1.val == node2.val &&
        treeEqual(node1.left, node2.left) &&
        treeEqual(node1.right, node2.right);
}