编辑代码

const findFirstNode = (nodeList) => {
    const ids = nodeList.map(item => item.id);
    const nextIds = nodeList.map(item => item.nextId);
    let headNo = [];
    for (var i = 0; i < nextIds.length; i++) {
        console.log('nextIds', nextIds[i]);
        if (!ids.includes(nextIds[i])) {
            headNo.push(nextIds[i]);
        }
    }
    if (!headNo.length) {
        throw Error('该链表是环状');
    }
    if (headNo.length > 1) {
        throw Error('存在节点不在链表内');
    }
    return headNo[0];
}
const list = [{ "id": 3, "nextId": 0 }, { "id": 1, "nextId": 2 }, { "id": 2, "nextId": 3 }];
console.log(findFirstNode(list));