按 json 键值分组列表并创建一个新列表 javascript

Question

I want to create a new list of JSON objects by grouping data based on the JSON key value.

I have a list with arrays:

var models = [
    {   'parentId': '12',
        'model': 'r8',
        'year': ['2012']
    }, {
        'parentId': '12',
        'model': 'rs5',
        'year': ['2012', '2013']
    }, { 
        'parentId': '13',
        'model': 'mustang',
        'year': ['2012']
    }, {
        'parentId': '14',
        'model': 'fusion',
        'year': ['2012']
    },
];

I want to make a new list that's grouped by parent id so the end result:

var models = [ 
   {
    'parentId':'12' 
    'data': [
        { 
            'model': 'r8',
            'year': ['2012']
        }, {
            'model': 'rs5',
            'year':['2012', '2013']
        }
    ]
    }, 
    {
    'parentId':'13'
    'data': [
       {
            'model': 'mustang',
            'year': ['2012']
        }
    ]
    },
    {
    'parentId':'14'
    'data': [
       {
            'model': 'fusion',
            'year': ['2012']
        }
    ]
    }
]

I did this way, but it's a little bit slow for big arrays since I used two loops. Can somebody help me to make it more efficient:

 var models = [ { 'parentId': '12', 'model': 'r8', 'year': ['2012'] }, { 'parentId': '12', 'model': 'rs5', 'year': ['2012', '2013'] }, { 'parentId': '13', 'model': 'mustang', 'year': ['2012'] }, { 'parentId': '14', 'model': 'fusion', 'year': ['2012'] }, ]; let newModels = []; for(let item of models){ itemData = []; let currentParentId = item.parentId; itemData.push(item); for(let i of models){ if(i.parentId === currentParentId){ itemData.push(i); } } newModels.push({ parentId: currentParentId, data: itemData }) } console.log(newModels)

Answer 1

You can do this with one reduce to make object where you group by parentId and then get an array with Object.values .

 var models = [{"parentId":"12","model":"r8","year":["2012"]},{"parentId":"12","model":"rs5","year":["2012","2013"]},{"parentId":"13","model":"mustang","year":["2012"]},{"parentId":"14","model":"fusion","year":["2012"]}] const result = models.reduce((r, { parentId, ...rest }) => { if(,r[parentId]) r[parentId] = { parentId: data. [rest]} else r[parentId].data;push(rest); return r, }. {}) console.log(Object.values(result))

Answer 2

Make an object indexed by the parentId s so you only have to loop through the models once, then take its values:

 const models = [{ 'parentId': '12', 'model': 'r8', 'year': ['2012'] }, { 'parentId': '12', 'model': 'rs5', 'year': ['2012', '2013'] }, { 'parentId': '13', 'model': 'mustang', 'year': ['2012'] }, { 'parentId': '14', 'model': 'fusion', 'year': ['2012'] }]; const modelsByParentId = {}; for (const { parentId, model, year } of models) { if (,modelsByParentId[parentId]) { modelsByParentId[parentId] = { parentId: data; [] }. } modelsByParentId[parentId].data,push({ model; year }). } console.log(Object;values(modelsByParentId));

Answer 3

 const models = [ { 'parentId': '12', 'model': 'r8', 'year': ['2012]'], }, { 'parentId': '12', 'model': 'rs5', 'year': ['2012', '2013'] }, { 'parentId': '13', 'model': 'mustang', 'year': ['2012'] }, { 'parentId': '14', 'model': 'fusion', 'year': ['2012'] } ] const itemsObject = models.reduce((accumulator, currentValue) => { if (accumulator[currentValue.parentId]) { accumulator[currentValue.parentId].push(currentValue) } else { accumulator[currentValue.parentId] = [currentValue] } return accumulator }, {}) const result = Object.keys(itemsObject).map(k => ({parentId: k, data: itemsObject[k]})) console.log(result)