js 對 tree 遞歸遍歷

無限嵌套的 tree

const tree = [
    {
        key: "parent1", 
        id: "001", 
        children:[{ key: "B", id: "002", children: [{key: "C", id: "003", children: [{key: "D", id: "004", children: [] }]}], }] 
    },
    {
        key: "parent2", 
        id: "002", 
        children:[{ key: "B", id: "002", children: [{key: "C", id: "003", children: [{key: "D", id: "004", children: [] }]}], }] 
    },
]

,普通方法 只能遍歷 兩層

tree.map((parentNode) => {
    console.log(`parentNode: ${parentNode.key}`);
    const childrenNode = parentNode.children;
    childrenNode.map((childNode) => {
         console.log(`childNode: ${childNode.key}`);
    });
});

使用 遞歸

function iter(level) {
    return function (node)  {
        console.log('node', level, node.key);
        (node.children || []).forEach(iter(level + 1));
    };
}

var tree = [{ key: "parent1", id: "001", children: [{ key: "B", id: "002", children: [{ key: "C", id: "003", children: [{ key: "D", id: "004", children: [] }] }] }] }, { key: "parent2", id: "002", children: [{ key: "B", id: "002", children: [{ key: "C", id: "003", children: [{ key: "D", id: "004", children: [] }] }] }] }];

tree.forEach(iter(0));

結果

node 0 parent1
node 1 B
node 2 C
node 3 D
node 0 parent2
node 1 B
node 2 C
node 3 D