扁平数据和树状数据结构的互相转换

扁平结构转换成树状结构

const list = [
    { id: 1, parentId: null },
    { id: 2, parentId: null },
    { id: 12, parentId: 1 },
];

function bullTree (list) {
    const temp = {};
    const tree = [];
    for (let item of list) {
        temp[item.id] = item;    
    }
    for (let i in temp) {
        // 当前节点
        const currentNode = temp[i];
        if (currentNode.parentId) {
            // 非顶层节点
            const currentParentNode = temp[currentNode.parentId];
            if (currentParentNode) {
                // 当前节点的父节点存在
                if (!currentParentNode.children) {
                    currentParentNode.children = [];                
                }
                currentParentNode.children.push(currentNode);          
            }      
        } else {
            // 顶层节点
            tree.push(currentNode); 
        } 
    }
}

树状结构转换成扁平结构

这里用到了递归的方式。

function buildList (tree) {
    let list = [];
    tree.forEach((item) => {
        const [ children, ...rest ] = item;
        list.push(rest);
        if (children) {
            list = list.concat(buildList(children));      
        }
    });
    return list;
}