JavaScript Map / Reduce 按计数分组返回

Question

我有一个 JSON 集合作为数组。我想按集合中的三个字段分组，然后返回结果以及匹配文档的数量。下面的示例有望使其更清晰。

返回的 JSON 文档集合：

[
    {
        _id: 1,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 2,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 3,
       browser: 'opera',
       ipAddress: '222.0.888.0',
       uri: 'example1.com'
    },
    {
       _id: 4,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 5,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 6,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 7,
       browser: 'opera',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    }
]

应该对浏览器、ipAddress 和 uri 进行分组，然后返回分组结果以及下面的计数（我检查了几次，所以我希望下面的数字加起来就是上面每个组合的实例！）。

[
    {
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com',
       count: 2
    },
    {
       browser: 'opera',
       ipAddress: '222.0.888.0',
       uri: 'example1.com',
       count: 1
    },
    {
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com',
       count: 3
    },
       browser: 'opera',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com',
       count: 1
]

我知道使用 map/reduce 应该很容易做到这一点，但我似乎无法让我的大脑困惑如何做到这一点！

提前致谢。

Answer 1

使用lodash 的另一种（更实用的）方法：

_(array).groupBy(v => ([v.browser, v.ipAddress, v.uri]))
        .map(v => _.merge(_.omit(v[0], '_id'), {count: v.length}))
        .value();

简短说明：groupBy 使用浏览器、ipAddress 和 uri 创建分组。在map 语句中，我们删除了 _id 字段并根据组中对象的数量添加计数。

Answer 2

如果你愿意使用lodash（如果没有最好使用），你可以这样做，

var array = [
    {
        _id: 1,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 2,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 3,
       browser: 'opera',
       ipAddress: '222.0.888.0',
       uri: 'example1.com'
    },
    {
       _id: 4,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 5,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 6,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 7,
       browser: 'opera',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    }
]

var res = _.reduce(array, function(acc, elem){
  delete elem._id;
  var obj = _.find(acc, elem)
  if(obj){
    obj.count++;
  }
  else{
    elem.count = 1;
    acc.push(elem);
  }
  return acc;
}, [])

console.log(res);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

Answer 3

你可以试试这样的：

var data=[{_id:1,browser:"chrome",ipAddress:"222.111.111.0",uri:"example1.com"},{_id:2,browser:"chrome",ipAddress:"222.111.111.0",uri:"example1.com"},{_id:3,browser:"opera",ipAddress:"222.0.888.0",uri:"example1.com"},{_id:4,browser:"chrome",ipAddress:"222.111.222.0",uri:"sample1.com"},{_id:5,browser:"chrome",ipAddress:"222.111.222.0",uri:"sample1.com"},{_id:6,browser:"chrome",ipAddress:"222.111.222.0",uri:"sample1.com"},{_id:7,browser:"opera",ipAddress:"222.111.222.0",uri:"sample1.com"}];

function groupBy(array, keys) {
  var groups = array.reduce(function(p, c) {
    var hash = keys.map(function(k){ return c[k]; }).join("|")
    p[hash] = p[hash] || c;
    p[hash]["count"] = (p[hash]["count"] || 0) + 1
    delete p[hash]["_id"];
    return p;
  }, {});
  var result = Object.keys(groups).map(function(x){return groups[x] })
  console.log(result);
  return result
}

var keys = ["browser", "ipAddress", "uri"]
groupBy(data, keys)

Answer 4

您可以通过 vanilla JavaScript 使用单个 reduce 来做到这一点：

let arr = [
    {
        _id: 1,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 2,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 3,
       browser: 'opera',
       ipAddress: '222.0.888.0',
       uri: 'example1.com'
    },
    {
       _id: 4,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 5,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 6,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 7,
       browser: 'opera',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    }
]

let result = arr.reduce((_, x) => {
  for(let i = 0; i < _.length; i++) {
    if(_[i].browser === x.browser && _[i].ipAddress === x.ipAddress && _[i].uri === x.uri) {
      _[i].count++
      return _
    }
  }
  let { _id, ...rest } = x
  return [ ..._, { ...rest, count: 1 } ]
}, [])

console.log(result)

Answer 5

您可以通过使用通用 reducer 生成器来实现这一点。此代码基于 my previous answer to another question 。你可以给它你想要分组的字段，它返回的函数可以作为减速器给出一个项目计数。

let arr = Object.freeze([
    {
        _id: 1,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 2,
       browser: 'chrome',
       ipAddress: '222.111.111.0',
       uri: 'example1.com'
    },
    {
       _id: 3,
       browser: 'opera',
       ipAddress: '222.0.888.0',
       uri: 'example1.com'
    },
    {
       _id: 4,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 5,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 6,
       browser: 'chrome',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    },
    {
       _id: 7,
       browser: 'opera',
       ipAddress: '222.111.222.0',
       uri: 'sample1.com'
    }
]);

const groupByReducerCount = (group) =>
  (result, row) => {
    const keygroup = group.map((v) => row[v]);
    const key = keygroup.join(':');
    if (result[key])
      result[key] ++;
    else
      result[key] = 1;
    return result;
  };


const result = arr.reduce(groupByReducerCount(['uri','browser','ipAddress']),{});

console.log(result)