javascript - 如何在我的案例中将数组存储在对象中

Question

我正在尝试将项目推送到数组。

我有类似的东西

var t = [];
items = [
    {id:123, name:'test1', category:'toy'},
    {id:123, name:'test2', category:'cookies'},
    {id:789, name:'test3', category:'toy'},
    {id:155, name:'test4', category:'pen'},
    {id:155, name:'test5', category:'eraser'}
];

items.map(function(item) {    
    t[item.id].push(item.category);
    //do other things
})

我需要的最终结果

t = [
    {123: ['toy', 'cookies']},
    {789: ['toy']},
    {155: ['pen', 'eraser']}
]

我无法读取未定义的属性“push”。 有更好的办法来解决这个问题吗？多谢!

Answer 1

使用t作为对象而不是数组，每个对象都会有一个数组值，并且之前也必须分配该值，尝试:

var t = {}, items = [
    {id:123, name:'test1', category:'toy'},
    {id:123, name:'test2', category:'cookies'},
    {id:789, name:'test3', category:'toy'},
    {id:155, name:'test4', category:'pen'},
    {id:155, name:'test5', category:'eraser'}
];

items.forEach(function(item){
  !t[item.id] && (t[item.id] = []);
  t[item.id].push(item.category)
})

document.write(JSON.stringify(t));
document.write("<br><b>" + t[123] + "</b>"); //<= Get items by ID

//In your case
var tArray = [];
for(var id in t){
  var obj = {};
  obj[id] = t[id];
  tArray.push(obj)
}
document.write("<br>" + JSON.stringify(tArray));