数组与树相互转换

const arr = [
    { id: 0, name: '新闻' },
    { id: 1, name: '体育', parentId: 0 },
    { id: 2, name: '篮球', parentId: 1 },
    { id: 3, name: '足球', parentId: 1 },
    { id: 4, name: 'NBA', parentId: 2 },
    { id: 5, name: 'CBA', parentId: 2 },
    { id: 6, name: '娱乐', parentId: 0 },
    { id: 7, name: '小品', parentId: 6 },
    { id: 8, name: '相声', parentId: 6 },
]

function array2Tree(sourceArr) {
    const mapping = new Map();
    const result = [];

    sourceArr.forEach(element => {
        mapping.set(element.id, element);
    });

    sourceArr.forEach(element => {
        const parent = mapping.get(element.parentId);
        if (!parent) {
            result.push(element);
            return;
        };
        (parent.children || (parent.children = [])).push(element);
    });

    return result;
}

console.log('tree', array2Tree(arr));

function tree2Array(sourceTree) {
    const result = [];
    const queue = Array.isArray(sourceTree) ? sourceTree : [sourceTree];

    while(queue.length) {
        const firstElement = queue.shift();
        result.push({
            id: firstElement.id,
            parentId: firstElement.parentId,
            name: firstElement.name
        });

        queue.push(...(firstElement.children || []));
    }

    return result;
}