Question

大家好，请您帮我减少数组。我有两个数组，我需要在中期将其中一个分组。在这里您可以找到示例

我有对象数组

const arr = [{
    mid: 888,
    name: "test"
  },
  {
    mid: 888,
    name: "test1"
  },
  {
    mid: 888,
    name: "test2"
  },
  {
    mid: 777,
    name: "test10"
  },
]

但是我需要中途分组并得到类似的东西

const arr = [{
    mid: 888,
    projects: [{
        name: "test"
      },
      {
        name: "test1"
      },
      {
        name: "test2"
      },
    ]
  },
  {
    mid: 777,
    projects: [{
      name: "test10"
    }, ]
  }
]

Answer 1

const arr = [{
    mid: 888,
    name: "test"
  },
  {
    mid: 888,
    name: "test1"
  },
  {
    mid: 888,
    name: "test2"
  },
  {
    mid: 777,
    name: "test10"
  }
];

let newArray = []
arr.map(item => item.mid).filter((value, index, self)=> { 
    return self.indexOf(value) === index;
}).forEach((mid)=>{
    newArray.push({
        mid,
        projects: arr.filter(item => item.mid == mid).map(item =>{ return {name: item.name}; })
    })
})

console.log(newArray)

使用reduce的其他方式：

const arr = [{
    mid: 888,
    name: "test"
  },
  {
    mid: 888,
    name: "test1"
  },
  {
    mid: 888,
    name: "test2"
  },
  {
    mid: 777,
    name: "test10"
  }
];

newArray = arr.map(item => item.mid).filter((value, index, self)=> { 
    return self.indexOf(value) === index;
}).map(item=> { return {mid: item, projects: []}})

newArray = arr.reduce((res, current)=>{
    let index = newArray.map(item => item.mid).indexOf(current.mid);
    res[index].projects.push({name: current.name})
    
    return res;
}, newArray)

console.log(newArray)

Answer 2

这不是最快的方法，但是可以通过对代码段进行试验来帮助更好地理解reduce函数* JsFiddle

let arr = [{
    mid: 888,
    name: 'test'
  },
  {
    mid: 888,
    name: 'test1'
  },
  {
    mid: 888,
    name: 'test2'
  },
  {
    mid: 777,
    name: 'test10'
  },
]

let reduced = arr.reduce((prev, now) => {
  // first iteration, prev == []
  // now == { mid: 888, name: 'test' }
  let index = prev.map(e => e.mid).indexOf(now.mid);
  if (~index) { // if index found
    prev[index].projects.push({
      name: now.name
    })
  } else {
    prev.push({
      mid: now.mid,
      projects: [{
        name: now.name
      }]
    })
  }
  return prev;
}, []); /* Starting from empty array */

console.log( reduced );

Answer 3

您可以像这样将其分组。

var groupedData = _.mapValues(_.groupBy(arr, 'mid'),
                      clist => clist.map(car => _.omit(car, 'mid')));

结果将是

{888: [{
    name: test
  },
  {
    name: test1
  },
  {
    name: test2
  },
],
777: [{
  name: test10
} ]}

Answer 4

这是一个reduce函数如何使用filter和三进制大小来完成技巧：

const arr = [{mid: 888,name: "test"},
  {mid: 888,name: "test1"},
  {mid: 888, name: "test2"},
  {mid: 777, name: "test10"}];

let newArray = arr.reduce(function (r, row) {
    let dt = r.filter(x => x.mid == row.mid);
    dt.length ? dt[0].projects.push(row.name): r.push({mid: row.mid, projects: [row.name]});
    return r;
}, []);

console.log(newArray);

如何按ID数组分组

4 个答案: