树转数组,用递归

const list = [
                    { id: 1, value: 1 },
                    { id: 2, value: 2, parentId: 1 },
                    { id: 3, value: 3, parentId: 1 },
                    { id: 4, value: 4, parentId: 2 },
                    { id: 5, value: 7, parentId: 4 },
            ]
const tree = {
        id: 1,
        value: 1,
        children: [
                {
                        id: 2,
                        value: 2,
                        parentId: 1,
                        children: [
                                {
                                        id: 4,
                                        value: 4,
                                        parentId: 2,
                                        children: [
                                                {
                                                        id: 5,
                                                        value: 7,
                                                        parentId: 4,
                                                        children: [],
                                                },
                                        ],
                                },
                        ],
                },
                {
                        id: 3,
                        value: 3,
                        parentId: 1,
                        children: [],
                },
        ],
}
                        
    function treeToArr(tree) {
            const arr = []
            function traverse(node, parentId = null) {
                    arr.push({
                            id: node.id,
                            value: node.value,
                            parentId: parentId
                    })
                    if(node.children && node.children.length) {
                            node.children.forEach(item => {
                            // 以父id作为子项的parentId
                                    traverse(item, node.id)
                            })
                    }
            }
            traverse(tree)
            return arr
    }

    console.log(treeToArr(tree))