如何在reactjs/javascript中按值对对象数组进行分组

Question

我有一个具有不同值的对象数组

 items=[{id:1,category:"cat_1" , title:"My title 1"},{id:2,category:"cat_2" , title:"My title 2"},{id:6,category:"cat_1" , title:"Another title 1"},{id:1,category:"cat_3" , title:"My title 3"},{id:8,category:"cat_1" , title:"Third Title"},{id:2,category:"cat_2" , title:"Another title 2 "}]

我使用数组映射列出对象并将其显示为

     {
     items.map((item) => (
        <h1>{item.category}</h1>
        <p>{item.title}</p>
    ))} 

我的问题是如何迭代项目,以便按类别对项目进行分组,如下所示

cat_1
- My title 1
- Another title 1
- My title 3

cat_2
- My title 2
- Another title 2

cat_3
-Third Title

Answer 1

用途.reduce:

const items = [{
  id: 1,
  category: "cat_1",
  title: "My title 1"
}, {
  id: 2,
  category: "cat_2",
  title: "My title 2"
}, {
  id: 6,
  category: "cat_1",
  title: "Another title 1"
}, {
  id: 1,
  category: "cat_3",
  title: "My title 3"
}, {
  id: 8,
  category: "cat_1",
  title: "Third Title"
}, {
  id: 2,
  category: "cat_2",
  title: "Another title 2 "
}];
const cats = items.reduce((catsSoFar, { category, title }) => {
  if (!catsSoFar[category]) catsSoFar[category] = [];
  catsSoFar[category].push(title);
  return catsSoFar;
}, {});
console.log(cats);

Answer 2

我在很多项目中使用 lodash 作为通用实用带。如果你决定做类似的事情——那就很简单：

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const data = [{\r\n  id: 1,\r\n  category: "cat_1",\r\n  title: "My title 1"\r\n}, {\r\n  id: 2,\r\n  category: "cat_2",\r\n  title: "My title 2"\r\n}, {\r\n  id: 6,\r\n  category: "cat_1",\r\n  title: "Another title 1"\r\n}, {\r\n  id: 1,\r\n  category: "cat_3",\r\n  title: "My title 3"\r\n}, {\r\n  id: 8,\r\n  category: "cat_1",\r\n  title: "Third Title"\r\n}, {\r\n  id: 2,\r\n  category: "cat_2",\r\n  title: "Another title 2 "\r\n}];\r\n\r\nconst groups = _.groupBy(data, \xc2\xa0\'category\');\r\n\r\nconsole.log(groups);

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<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.5/lodash.min.js"></script>

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