const data = [
    { id: 56, parentId: 62 },
    { id: 81, parentId: 80 },
    { id: 74, parentId: null },
    { id: 76, parentId: 80 },
    { id: 63, parentId: 62 },
    { id: 80, parentId: 86 },
    { id: 87, parentId: 86 },
    { id: 62, parentId: 74 },
    { id: 86, parentId: 74 },
];
const idMapping = data.reduce((acc, el, i) => {
    acc[el.id] = i;
    return acc;
}, {});
let root;
data.forEach(el => {
    // 判断根节点
    if (el.parentId === null) {
        root = el;
        return;
    }
    // 用映射表找到父元素
    const parentEl = data[idMapping[el.parentId]];
    // 把当前元素添加到父元素的`children`数组中
    parentEl.children = [...(parentEl.children || []), el];
});
console.log(root);

const data = [
    { id: 56, parentId: 62 },
    { id: 81, parentId: 80 },
    { id: 74, parentId: null },
    { id: 76, parentId: 80 },
    { id: 63, parentId: 62 },
    { id: 80, parentId: 86 },
    { id: 87, parentId: 86 },
    { id: 62, parentId: 74 },
    { id: 86, parentId: 74 },
];
const idMapping = data.reduce((acc, el, i) => {
    acc[el.id] = i;
    return acc;
}, {});
let root;
data.forEach(el => {
    // 判断根节点
    if (el.parentId === null) {
        root = el;
        return;
    }
    // 用映射表找到父元素
    const parentEl = data[idMapping[el.parentId]];
    // 把当前元素添加到父元素的`children`数组中
    parentEl.children = [...(parentEl.children || []), el];
});
console.log(root);