javascript - 通过javascript重新排序数组对象

Question

我已经做了一些排序，但仍然不明白为什么结果是[]。你们能帮我解决我缺少的东西吗？

我有我的原始数组对象:

var data = [
 {message:'hello', username:'user1'},
 {message:'data', username:'user1'},
 {message:'sample', username:'user2'},
 {message:'here', username:'user2'},
];

我的功能是:

var chat = [];
function reorder(obj) {
    obj.forEach( function(val, i) {
        if(typeof chat[val.username] === 'undefined') {
            chat[val.username] = [];
            chat[val.username].push(val);   
        }
        else 
            chat[val.username].push(val);
    });
    return chat;
}

在我的控制台上:

reorder(data);

我期望有:

var data2 = [
  'user1': [{message:'hello', username:'user1'}, {message:'data', username:'user1'} ],
  'user2': [{message:'sample', username:'user2'}, {message:'here', username:'user2'} ],
];

Answer 1

您可以使用reduce轻松完成此操作:

var data2 = data.reduce(function(acc, x) {
  acc[x.username] = (acc[x.username] || []).concat(x)
  return acc
},{})
/*^
{ user1: 
   [ { message: 'hello', username: 'user1' },
     { message: 'data', username: 'user1' } ],
  user2: 
   [ { message: 'sample', username: 'user2' },
     { message: 'here', username: 'user2' } ] }
*/