如何在一个键下对 JSON 数组中的所有对象的键下存在的值进行分组？

Question

I have an array of JSON like:

[
   {user_id:1, name: "Person A", project: "Project A"},
   {user_id:1, name: "Person A", project: "Project B"},
   {user_id:2, name: "Person B", project: "Project A"},
   {user_id:2, name: "Person B", project: "Project C"},
   {user_id:3, name: "Person C", project: "Project D"}
]

I want to transform this array such that there's only one entry for a person and it has an array with value active_projects or something with all his projects. Basically I want to remove the redundancy in this array. The output would be:

[
   {user_id:1, name: "Person A", active_projects: ["Project A","Project B"] },
   {user_id:2, name: "Person B", active_projects: ["Project A","Project C"] },
   {user_id:3, name: "Person C", active_projects: ["Project D"] }
]

What is the cleanest and best approach for this?

Answer 1

A simple solution would be to first compute a map of the user_ids using reduce . Then simply use Object.values to turn it into an array.

 const lkp = data.reduce((acc, {user_id, name, project}) => { acc[user_id] = acc[user_id] || {}; acc[user_id].user_id = user_id; acc[user_id][name] = name; acc[user_id].active_projects = acc[user_id].active_projects || []; acc[user_id].active_projects.push(project); return acc; }, {}) const arr = Object.values(lkp) console.log(arr)

 <script> var data = [ {user_id:1, name: "Person A", project: "Project A"}, {user_id:1, name: "Person A", project: "Project B"}, {user_id:2, name: "Person B", project: "Project A"}, {user_id:2, name: "Person B", project: "Project C"}, {user_id:3, name: "Person C", project: "Project D"} ]; </script>

Answer 2

You can try reduce method of JavaScript.

 var data =[ {user_id:1, name: "Person A", project: "Project A"}, {user_id:1, name: "Person A", project: "Project B"}, {user_id:2, name: "Person B", project: "Project A"}, {user_id:2, name: "Person B", project: "Project C"}, {user_id:3, name: "Person C", project: "Project D"}]; result = Object.values(data.reduce((acc, {user_id, project, ...rest})=>{ acc[user_id] = acc[user_id] || { user_id, ...rest }; acc[user_id].activeProject = acc[user_id].activeProject || []; acc[user_id].activeProject.push(project); return acc; },{})); console.log(result);