//树形数据铺成数组

tree2arr(tree) {
        let arr = []
        const expanded = datas => {
            if (datas && datas.length > 0) {
                datas.forEach(e => {
                    arr.push(e)
                    expanded(e.children)
                })
            }
        }
        expanded(tree)
        return arr
    }

// 数组拼成树形数据

arr2tree(data) {
        let result = []
        if (!Array.isArray(data)) {
            return result
        }
        data.forEach(item => {
            delete item.children;
        });
        let map = {};
        data.forEach(item => {
            map[item.id] = item;
        });
        data.forEach(item => {
            let parent = map[item.pid];
            if (parent) {
                (parent.children || (parent.children = [])).push(item);
            } else {
                result.push(item);
            }
        });
        return result;
    }