JavaScript：如何在两个输入数组上对基于二维数组的匹配字段进行分组？

Question

我有以下数组a，b如图所示？

var a = [
  {id: 1, name: "phone"},
  {id: 2,  name: "nick"}
];

var b = [
  {id: 7, parentId: 1, name: "phone_item1"},
  {id: 8, parentId: 2, name: "phone_item2"},
  {id: 9, parentId: 1, name: "nick_item1"},
  {id: 10, parentId: 2, name: "nick_item2"}
];

//You want to filter by A array id
const filterIds = a.map(({ id }) => id);

//My attempt
const c = Object.values(b.reduce((r, c) => {
  r[c.parentId] = r[c.parentId] || [];
  r[c.parentId].push(c);
  return r;
}, {}));

console.log(c)

我正在尝试获取以下二维数组：

[[
  {id: 7, parentId: 1, name: "phone_item1"},
  {id: 9, parentId: 1, name: "nick_item1"}
],[
  {id: 8, parentId: 2, name: "phone_item2"},
  {id: 10, parentId: 2, name: "nick_item2"}
]]

生成的数组应该根据idarray a与parentIdof 的比较b，这样才能得到2D数组的这种样式。由于某种原因，我的尝试无法正常工作-您可以帮我吗？

Answer 1

如果我在这里遗漏了一些东西，不要担心-假设我正确理解了您的问题，一个简单的实现就是映射每一项，a以使映射返回bon匹配项之间的过滤后的子集bItem.parentId === aItem.id（其中aItem和bItem分别迭代各个列表的项） ：

var a = [
  {id: 1, name: "phone"},
  {id: 2,  name: "nick"}
];

var b = [
  {id: 7, parentId: 1, name: "phone_item1"},
  {id: 8, parentId: 2, name: "phone_item2"},
  {id: 9, parentId: 1, name: "nick_item1"},
  {id: 10, parentId: 2, name: "nick_item2"}
];

/* Map each item in a to a classification of b against a */
const result = a.map(aItem => {

  /* For current aItem, return a subset of b, filtered by matches 
  on bItem.parentId === aItem.id (ie the classification criteria) */
  return b.filter(bItem => bItem.parentId === aItem.id)
});

console.log(result)