对对象数组进行分组的最有效方法

2020/09/24 20:41 · javascript ·  · 0评论

在数组中对对象进行分组的最有效方法是什么?

例如,给定此对象数组:

[ 
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
]

我正在表中显示此信息。我想对不同的方法进行分组,但是我想对这些值求和。

我将Underscore.js用于其groupby函数,这很有用,但并不能解决所有问题,因为我不希望它们“分裂”而是“合并”,更像SQL group by方法。

我正在寻找的是能够总计特定值(如果需要)。

因此,如果我进行groupby Phase,我希望收到:

[
    { Phase: "Phase 1", Value: 50 },
    { Phase: "Phase 2", Value: 130 }
]

如果我进行了分组Phase/ Step则会收到:

[
    { Phase: "Phase 1", Step: "Step 1", Value: 15 },
    { Phase: "Phase 1", Step: "Step 2", Value: 35 },
    { Phase: "Phase 2", Step: "Step 1", Value: 55 },
    { Phase: "Phase 2", Step: "Step 2", Value: 75 }
]

是否为此提供了有用的脚本,还是应该坚持使用Underscore.js,然后循环遍历生成的对象来自己做总计?

如果要避免使用外部库,则可以简洁地实现groupBy()如下所示的原始版本

var groupBy = function(xs, key) {
  return xs.reduce(function(rv, x) {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

console.log(groupBy(['one', 'two', 'three'], 'length'));

// => {3: ["one", "two"], 5: ["three"]}

使用ES6 Map对象:

/**
 * @description
 * Takes an Array<V>, and a grouping function,
 * and returns a Map of the array grouped by the grouping function.
 *
 * @param list An array of type V.
 * @param keyGetter A Function that takes the the Array type V as an input, and returns a value of type K.
 *                  K is generally intended to be a property key of V.
 *
 * @returns Map of the array grouped by the grouping function.
 */
//export function groupBy<K, V>(list: Array<V>, keyGetter: (input: V) => K): Map<K, Array<V>> {
//    const map = new Map<K, Array<V>>();
function groupBy(list, keyGetter) {
    const map = new Map();
    list.forEach((item) => {
         const key = keyGetter(item);
         const collection = map.get(key);
         if (!collection) {
             map.set(key, [item]);
         } else {
             collection.push(item);
         }
    });
    return map;
}


// example usage

const pets = [
    {type:"Dog", name:"Spot"},
    {type:"Cat", name:"Tiger"},
    {type:"Dog", name:"Rover"}, 
    {type:"Cat", name:"Leo"}
];
    
const grouped = groupBy(pets, pet => pet.type);
    
console.log(grouped.get("Dog")); // -> [{type:"Dog", name:"Spot"}, {type:"Dog", name:"Rover"}]
console.log(grouped.get("Cat")); // -> [{type:"Cat", name:"Tiger"}, {type:"Cat", name:"Leo"}]

关于地图:https
//developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Map

使用ES6:

const groupBy = (items, key) => items.reduce(
  (result, item) => ({
    ...result,
    [item[key]]: [
      ...(result[item[key]] || []),
      item,
    ],
  }), 
  {},
);

尽管linq的答案很有趣,但它也很笨重。我的方法有些不同:

var DataGrouper = (function() {
    var has = function(obj, target) {
        return _.any(obj, function(value) {
            return _.isEqual(value, target);
        });
    };

    var keys = function(data, names) {
        return _.reduce(data, function(memo, item) {
            var key = _.pick(item, names);
            if (!has(memo, key)) {
                memo.push(key);
            }
            return memo;
        }, []);
    };

    var group = function(data, names) {
        var stems = keys(data, names);
        return _.map(stems, function(stem) {
            return {
                key: stem,
                vals:_.map(_.where(data, stem), function(item) {
                    return _.omit(item, names);
                })
            };
        });
    };

    group.register = function(name, converter) {
        return group[name] = function(data, names) {
            return _.map(group(data, names), converter);
        };
    };

    return group;
}());

DataGrouper.register("sum", function(item) {
    return _.extend({}, item.key, {Value: _.reduce(item.vals, function(memo, node) {
        return memo + Number(node.Value);
    }, 0)});
});

您可以在JSBin上看到它的运行

has尽管我可能会错过它,但在Underscore中我看不到有任何功能可以做什么它与几乎相同_.contains,但是用于_.isEqual而不是===用于比较。除此之外,其余的都是特定于问题的,尽管尝试是通用的。

现在DataGrouper.sum(data, ["Phase"])返回

[
    {Phase: "Phase 1", Value: 50},
    {Phase: "Phase 2", Value: 130}
]

DataGrouper.sum(data, ["Phase", "Step"])返回

[
    {Phase: "Phase 1", Step: "Step 1", Value: 15},
    {Phase: "Phase 1", Step: "Step 2", Value: 35},
    {Phase: "Phase 2", Step: "Step 1", Value: 55},
    {Phase: "Phase 2", Step: "Step 2", Value: 75}
]

但是sum这里仅仅是一种潜在的功能。您可以根据需要注册其他人:

DataGrouper.register("max", function(item) {
    return _.extend({}, item.key, {Max: _.reduce(item.vals, function(memo, node) {
        return Math.max(memo, Number(node.Value));
    }, Number.NEGATIVE_INFINITY)});
});

现在DataGrouper.max(data, ["Phase", "Step"])会回来

[
    {Phase: "Phase 1", Step: "Step 1", Max: 10},
    {Phase: "Phase 1", Step: "Step 2", Max: 20},
    {Phase: "Phase 2", Step: "Step 1", Max: 30},
    {Phase: "Phase 2", Step: "Step 2", Max: 40}
]

或者如果您注册了此:

DataGrouper.register("tasks", function(item) {
    return _.extend({}, item.key, {Tasks: _.map(item.vals, function(item) {
      return item.Task + " (" + item.Value + ")";
    }).join(", ")});
});

然后打电话DataGrouper.tasks(data, ["Phase", "Step"])给你

[
    {Phase: "Phase 1", Step: "Step 1", Tasks: "Task 1 (5), Task 2 (10)"},
    {Phase: "Phase 1", Step: "Step 2", Tasks: "Task 1 (15), Task 2 (20)"},
    {Phase: "Phase 2", Step: "Step 1", Tasks: "Task 1 (25), Task 2 (30)"},
    {Phase: "Phase 2", Step: "Step 2", Tasks: "Task 1 (35), Task 2 (40)"}
]

DataGrouper本身就是一个功能。您可以使用数据和要分组的属性列表来调用它。它返回一个数组,该数组的元素是具有两个属性的对象:key是分组属性的集合,vals是包含不在键中的其余属性的对象的数组。例如,DataGrouper(data, ["Phase", "Step"])将产生:

[
    {
        "key": {Phase: "Phase 1", Step: "Step 1"},
        "vals": [
            {Task: "Task 1", Value: "5"},
            {Task: "Task 2", Value: "10"}
        ]
    },
    {
        "key": {Phase: "Phase 1", Step: "Step 2"},
        "vals": [
            {Task: "Task 1", Value: "15"}, 
            {Task: "Task 2", Value: "20"}
        ]
    },
    {
        "key": {Phase: "Phase 2", Step: "Step 1"},
        "vals": [
            {Task: "Task 1", Value: "25"},
            {Task: "Task 2", Value: "30"}
        ]
    },
    {
        "key": {Phase: "Phase 2", Step: "Step 2"},
        "vals": [
            {Task: "Task 1", Value: "35"}, 
            {Task: "Task 2", Value: "40"}
        ]
    }
]

DataGrouper.register接受一个函数并创建一个新函数,该函数接受初始数据和要分组的属性。然后,此新函数采用上述输出格式,并依次对每个函数运行您的函数,并返回一个新数组。生成的函数DataGrouper根据您提供的名称存储为的属性,如果只需要本地引用,也将返回该函数

嗯,这有很多解释。我希望代码相当简单明了!

我会检查lodash groupBy,它看起来确实可以满足您的需求。它也很轻巧,非常简单。

小提琴示例:https//jsfiddle.net/r7szvt5k/

假设您的数组名称是arr带有lodash的groupBy,则为:

import groupBy from 'lodash/groupBy';
// if you still use require:
// const groupBy = require('lodash/groupBy');

const a = groupBy(arr, function(n) {
  return n.Phase;
});
// a is your array grouped by Phase attribute

使用可能更容易做到linq.js这一点,它旨在真正实现LINQ in JavaScript(DEMO):

var linq = Enumerable.From(data);
var result =
    linq.GroupBy(function(x){ return x.Phase; })
        .Select(function(x){
          return {
            Phase: x.Key(),
            Value: x.Sum(function(y){ return y.Value|0; })
          };
        }).ToArray();

结果:

[
    { Phase: "Phase 1", Value: 50 },
    { Phase: "Phase 2", Value: 130 }
]

或者,更简单地使用基于字符串的选择器(DEMO):

linq.GroupBy("$.Phase", "",
    "k,e => { Phase:k, Value:e.Sum('$.Value|0') }").ToArray();

您可以Map构建ES6 array.reduce()

const groupedMap = initialArray.reduce(
    (entryMap, e) => entryMap.set(e.id, [...entryMap.get(e.id)||[], e]),
    new Map()
);

与其他解决方案相比,它具有一些优点:

  • 它不需要任何库(例如_.groupBy()
  • 您得到的是JavaScript Map而不是对象(例如,由返回_.groupBy())。这有很多好处,包括:

    • 它会记住最初添加项目的顺序,
    • 键可以是任何类型,而不仅仅是字符串。
  • A Map是比数组更有用的结果。但是,如果您确实想要一个数组数组,则可以调用Array.from(groupedMap.entries())(对于[key, group array]成对数组)或Array.from(groupedMap.values())(对于简单数组)。
  • 它非常灵活;通常,您计划对此地图进行下一步的任何操作都可以直接作为缩减的一部分来完成。

作为最后一点的例子,假设我有一个对象数组,我想通过id在(浅)合并,如下所示:

const objsToMerge = [{id: 1, name: "Steve"}, {id: 2, name: "Alice"}, {id: 1, age: 20}];
// The following variable should be created automatically
const mergedArray = [{id: 1, name: "Steve", age: 20}, {id: 2, name: "Alice"}]

为此,我通常会先按ID分组,然后合并每个结果数组。相反,您可以直接在中进行合并reduce()

const mergedArray = Array.from(
    objsToMerge.reduce(
        (entryMap, e) => entryMap.set(e.id, {...entryMap.get(e.id)||{}, ...e}),
        new Map()
    ).values()
);
_.groupBy([{tipo: 'A' },{tipo: 'A'}, {tipo: 'B'}], 'tipo');
>> Object {A: Array[2], B: Array[1]}

来自:http : //underscorejs.org/#groupBy

您可以使用Alasql JavaScript库来实现:

var data = [ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
             { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }];

var res = alasql('SELECT Phase, Step, SUM(CAST([Value] AS INT)) AS [Value] \
                  FROM ? GROUP BY Phase, Step',[data]);

在jsFiddle尝试这个示例

顺便说一句:在大型数组(100000条记录和更多)上,Alasql比Linq快。请参阅 jsPref的测试

注释:

  • 这里我将Value放在方括号中,因为VALUE是SQL中的关键字
  • 我必须使用CAST()函数将字符串值转换为数字类型。
Array.prototype.groupBy = function(keyFunction) {
    var groups = {};
    this.forEach(function(el) {
        var key = keyFunction(el);
        if (key in groups == false) {
            groups[key] = [];
        }
        groups[key].push(el);
    });
    return Object.keys(groups).map(function(key) {
        return {
            key: key,
            values: groups[key]
        };
    });
};

MDN 在其文档中包含此示例Array.reduce()

// Grouping objects by a property
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce#Grouping_objects_by_a_property#Grouping_objects_by_a_property

var people = [
  { name: 'Alice', age: 21 },
  { name: 'Max', age: 20 },
  { name: 'Jane', age: 20 }
];

function groupBy(objectArray, property) {
  return objectArray.reduce(function (acc, obj) {
    var key = obj[property];
    if (!acc[key]) {
      acc[key] = [];
    }
    acc[key].push(obj);
    return acc;
  }, {});
}

var groupedPeople = groupBy(people, 'age');
// groupedPeople is:
// { 
//   20: [
//     { name: 'Max', age: 20 }, 
//     { name: 'Jane', age: 20 }
//   ], 
//   21: [{ name: 'Alice', age: 21 }] 
// }

尽管该问题有一些答案,并且答案看起来有些复杂,但我建议使用香草Javascript进行嵌套嵌套(如果需要)Map

function groupBy(array, groups, valueKey) {
    var map = new Map;
    groups = [].concat(groups);
    return array.reduce((r, o) => {
        groups.reduce((m, k, i, { length }) => {
            var child;
            if (m.has(o[k])) return m.get(o[k]);
            if (i + 1 === length) {
                child = Object
                    .assign(...groups.map(k => ({ [k]: o[k] })), { [valueKey]: 0 });
                r.push(child);
            } else {
                child = new Map;
            }
            m.set(o[k], child);
            return child;
        }, map)[valueKey] += +o[valueKey];
        return r;
    }, [])
};

var data = [{ Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }];

console.log(groupBy(data, 'Phase', 'Value'));
console.log(groupBy(data, ['Phase', 'Step'], 'Value'));
.as-console-wrapper { max-height: 100% !important; top: 0; }

该解决方案采用任意函数(不是键),因此比上述解决方案更灵活,并允许使用箭头函数,这些箭头函数类似于LINQ中使用的lambda表达式

Array.prototype.groupBy = function (funcProp) {
    return this.reduce(function (acc, val) {
        (acc[funcProp(val)] = acc[funcProp(val)] || []).push(val);
        return acc;
    }, {});
};

注意:是否要扩展Array的原型由您决定。

大多数浏览器支持的示例:

[{a:1,b:"b"},{a:1,c:"c"},{a:2,d:"d"}].groupBy(function(c){return c.a;})

使用箭头功能(ES6)的示例:

[{a:1,b:"b"},{a:1,c:"c"},{a:2,d:"d"}].groupBy(c=>c.a)

上面的两个示例都返回:

{
  "1": [{"a": 1, "b": "b"}, {"a": 1, "c": "c"}],
  "2": [{"a": 2, "d": "d"}]
}

无突变:

const groupBy = (xs, key) => xs.reduce((acc, x) => Object.assign({}, acc, {
  [x[key]]: (acc[x[key]] || []).concat(x)
}), {})

console.log(groupBy(['one', 'two', 'three'], 'length'));
// => {3: ["one", "two"], 5: ["three"]}

我想建议我的方法。首先,分别分组和汇总。让我们声明典型的“分组依据”功能。它需要另一个函数来为每个要分组的数组元素生成“哈希”字符串。

Array.prototype.groupBy = function(hash){
  var _hash = hash ? hash : function(o){return o;};

  var _map = {};
  var put = function(map, key, value){
    if (!map[_hash(key)]) {
        map[_hash(key)] = {};
        map[_hash(key)].group = [];
        map[_hash(key)].key = key;

    }
    map[_hash(key)].group.push(value); 
  }

  this.map(function(obj){
    put(_map, obj, obj);
  });

  return Object.keys(_map).map(function(key){
    return {key: _map[key].key, group: _map[key].group};
  });
}

完成分组后,您可以根据需要汇总数据

data.groupBy(function(o){return JSON.stringify({a: o.Phase, b: o.Step});})
    /* aggreagating */
    .map(function(el){ 
         var sum = el.group.reduce(
           function(l,c){
             return l + parseInt(c.Value);
           },
           0
         );
         el.key.Value = sum; 
         return el.key;
    });

共同点是可行的。我已经在Chrome控制台中测试了此代码。并随时改善并发现错误;)

选中的答案-只是浅层分组。了解减少非常好。问题还提供了其他总计计算的问题。

这是一个通过某些字段来对象数组的REAL GROUP BY,带有1)计算的键名和2)通过提供所需键的列表并将其唯一值转换为根键(如SQL GROUP)来完成级联分组的完整解决方案BY做。

const inputArray = [ 
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
];

var outObject = inputArray.reduce(function(a, e) {
  // GROUP BY estimated key (estKey), well, may be a just plain key
  // a -- Accumulator result object
  // e -- sequentally checked Element, the Element that is tested just at this itaration

  // new grouping name may be calculated, but must be based on real value of real field
  let estKey = (e['Phase']); 

  (a[estKey] ? a[estKey] : (a[estKey] = null || [])).push(e);
  return a;
}, {});

console.log(outObject);

试玩estKey-您可以将一个以上的字段分组,添加其他汇总,计算或其他处理。

您也可以递归地对数据进行分组。例如,最初按分组Phase,然后按Step字段分组依此类推。此外,删除多余的脂肪数据。

const inputArray = [
{ Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
{ Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
{ Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
{ Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
{ Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
{ Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
{ Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
{ Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
  ];

/**
 * Small helper to get SHALLOW copy of obj WITHOUT prop
 */
const rmProp = (obj, prop) => ( (({[prop]:_, ...rest})=>rest)(obj) )

/**
 * Group Array by key. Root keys of a resulting array is value
 * of specified key.
 *
 * @param      {Array}   src     The source array
 * @param      {String}  key     The by key to group by
 * @return     {Object}          Object with grouped objects as values
 */
const grpBy = (src, key) => src.reduce((a, e) => (
  (a[e[key]] = a[e[key]] || []).push(rmProp(e, key)),  a
), {});

/**
 * Collapse array of object if it consists of only object with single value.
 * Replace it by the rest value.
 */
const blowObj = obj => Array.isArray(obj) && obj.length === 1 && Object.values(obj[0]).length === 1 ? Object.values(obj[0])[0] : obj;

/**
 * Recursive grouping with list of keys. `keyList` may be an array
 * of key names or comma separated list of key names whom UNIQUE values will
 * becomes the keys of the resulting object.
 */
const grpByReal = function (src, keyList) {
  const [key, ...rest] = Array.isArray(keyList) ? keyList : String(keyList).trim().split(/\s*,\s*/);
  const res = key ? grpBy(src, key) : [...src];
  if (rest.length) {
for (const k in res) {
  res[k] = grpByReal(res[k], rest)
}
  } else {
for (const k in res) {
  res[k] = blowObj(res[k])
}
  }
  return res;
}

console.log( JSON.stringify( grpByReal(inputArray, 'Phase, Step, Task'), null, 2 ) );

假设您有这样的事情:

[{id:1, cat:'sedan'},{id:2, cat:'sport'},{id:3, cat:'sport'},{id:4, cat:'sedan'}]

通过做这个:
const categories = [...new Set(cars.map((car) => car.cat))]

您将获得:
['sedan','sport']

说明:
1.首先,我们通过传递数组来创建一个新的Set。
由于Set仅允许唯一值,因此将删除所有重复项。

  1. 现在重复项不见了,我们将使用散布运算符将其转换回数组...

设置文档:https
:
//developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/设置传播操作员文档:https :
//developer.mozilla.org/en-US/docs/Web/JavaScript /参考/运算符/ Spread_syntax

这是一个使用ES6的令人讨厌且难以阅读的解决方案:

export default (arr, key) => 
  arr.reduce(
    (r, v, _, __, k = v[key]) => ((r[k] || (r[k] = [])).push(v), r),
    {}
  );

对于那些问这甚至如何工作的人,这里有一个解释:

  • 两者=>都有return

  • Array.prototype.reduce功能最多包含4个参数。这就是为什么要添加第五个参数的原因,因此我们可以使用默认值在参数声明级别为组(k)提供便宜的变量声明。(是的,这是巫术)

  • 如果当前组在上一次迭代中不存在,则创建一个新的空数组,((r[k] || (r[k] = []))数组将求值为最左边的表达式,换句话说,是一个现有数组或一个空数组,这就是为什么push在该表达式之后有一个立即数,因为无论哪种方式,您都会得到一个数组。

  • 当存在时return,逗号,运算符将舍弃最左边的值,并返回针对此场景进行了调整的前一组。

易于理解的相同功能版本是:

export default (array, key) => 
  array.reduce((previous, currentItem) => {
    const group = currentItem[key];
    if (!previous[group]) previous[group] = [];
    previous[group].push(currentItem);
    return previous;
  }, {});

编辑:

TS版本:

const groupBy = <T, K extends keyof any>(list: T[], getKey: (item: T) => K) =>
  list.reduce((previous, currentItem) => {
    const group = getKey(currentItem);
    if (!previous[group]) previous[group] = [];
    previous[group].push(currentItem);
    return previous;
  }, {} as Record<K, T[]>);
groupByArray(xs, key) {
    return xs.reduce(function (rv, x) {
        let v = key instanceof Function ? key(x) : x[key];
        let el = rv.find((r) => r && r.key === v);
        if (el) {
            el.values.push(x);
        }
        else {
            rv.push({
                key: v,
                values: [x]
            });
        }
        return rv;
    }, []);
}

这个输出数组。

根据先前的答案

const groupBy = (prop) => (xs) =>
  xs.reduce((rv, x) =>
    Object.assign(rv, {[x[prop]]: [...(rv[x[prop]] || []), x]}), {});

如果您的环境支持,那么使用对象传播语法会更好一些。

const groupBy = (prop) => (xs) =>
  xs.reduce((acc, x) => ({
    ...acc,
    [ x[ prop ] ]: [...( acc[ x[ prop ] ] || []), x],
  }), {});

这里,我们的化简器获取部分形成的返回值(从一个空对象开始),并返回一个对象,该对象由先前返回值的散布成员以及一个新成员组成,该新成员的密钥是根据当前受迭代者的值计算得出的prop并且其值是该道具的所有值以及当前值的列表。

Array.prototype.groupBy = function (groupingKeyFn) {
    if (typeof groupingKeyFn !== 'function') {
        throw new Error("groupBy take a function as only parameter");
    }
    return this.reduce((result, item) => {
        let key = groupingKeyFn(item);
        if (!result[key])
            result[key] = [];
        result[key].push(item);
        return result;
    }, {});
}

var a = [
	{type: "video", name: "a"},
  {type: "image", name: "b"},
  {type: "video", name: "c"},
  {type: "blog", name: "d"},
  {type: "video", name: "e"},
]
console.log(a.groupBy((item) => item.type));
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

让我们生成一个通用Array.prototype.groupBy()工具。仅出于多样性考虑,让我们对递归方法使用ES6奇特的散布算子进行一些Haskellesque模式匹配。另外,让我们Array.prototype.groupBy()接受一个回调,该回调将item(e),index(i)和所应用的array(a)作为参数。

Array.prototype.groupBy = function(cb){
                            return function iterate([x,...xs], i = 0, r = [[],[]]){
                                     cb(x,i,[x,...xs]) ? (r[0].push(x), r)
                                                       : (r[1].push(x), r);
                                     return xs.length ? iterate(xs, ++i, r) : r;
                                   }(this);
                          };

var arr = [0,1,2,3,4,5,6,7,8,9],
    res = arr.groupBy(e => e < 5);
console.log(res);

只是为了增加Scott Sauyet的答案,有人在评论中询问如何使用他的功能对value1,value2等进行分组,而不是仅对一个值进行分组。

只需要编辑他的求和函数:

DataGrouper.register("sum", function(item) {
    return _.extend({}, item.key,
        {VALUE1: _.reduce(item.vals, function(memo, node) {
        return memo + Number(node.VALUE1);}, 0)},
        {VALUE2: _.reduce(item.vals, function(memo, node) {
        return memo + Number(node.VALUE2);}, 0)}
    );
});

保留主要的(DataGrouper)不变:

var DataGrouper = (function() {
    var has = function(obj, target) {
        return _.any(obj, function(value) {
            return _.isEqual(value, target);
        });
    };

    var keys = function(data, names) {
        return _.reduce(data, function(memo, item) {
            var key = _.pick(item, names);
            if (!has(memo, key)) {
                memo.push(key);
            }
            return memo;
        }, []);
    };

    var group = function(data, names) {
        var stems = keys(data, names);
        return _.map(stems, function(stem) {
            return {
                key: stem,
                vals:_.map(_.where(data, stem), function(item) {
                    return _.omit(item, names);
                })
            };
        });
    };

    group.register = function(name, converter) {
        return group[name] = function(data, names) {
            return _.map(group(data, names), converter);
        };
    };

    return group;
}());

Ceasar的回答很好,但是仅适用于数组内部元素的内部属性(对于字符串,为长度)。

此实现的工作方式类似于:此链接

const groupBy = function (arr, f) {
    return arr.reduce((out, val) => {
        let by = typeof f === 'function' ? '' + f(val) : val[f];
        (out[by] = out[by] || []).push(val);
        return out;
    }, {});
};

希望这可以帮助...

从@ mortb,@ jmarceli回答以及从这篇文章中

我利用的优势是分组依据JSON.stringify()原始值的多个列的标识

没有第三方

function groupBy(list, keyGetter) {
    const map = new Map();
    list.forEach((item) => {
        const key = keyGetter(item);
        if (!map.has(key)) {
            map.set(key, [item]);
        } else {
            map.get(key).push(item);
        }
    });
    return map;
}

const pets = [
    {type:"Dog", age: 3, name:"Spot"},
    {type:"Cat", age: 3, name:"Tiger"},
    {type:"Dog", age: 4, name:"Rover"}, 
    {type:"Cat", age: 3, name:"Leo"}
];

const grouped = groupBy(pets,
pet => JSON.stringify({ type: pet.type, age: pet.age }));

console.log(grouped);

Lodash第三方

const pets = [
    {type:"Dog", age: 3, name:"Spot"},
    {type:"Cat", age: 3, name:"Tiger"},
    {type:"Dog", age: 4, name:"Rover"}, 
    {type:"Cat", age: 3, name:"Leo"}
];

let rslt = _.groupBy(pets, pet => JSON.stringify(
 { type: pet.type, age: pet.age }));

console.log(rslt);

具有 reduce基于ES6版本的功能的支持iteratee

如果iteratee未提供功能,则按预期方式工作

const data = [{id: 1, score: 2},{id: 1, score: 3},{id: 2, score: 2},{id: 2, score: 4}]

const group = (arr, k) => arr.reduce((r, c) => (r[c[k]] = [...r[c[k]] || [], c], r), {});

const groupBy = (arr, k, fn = () => true) => 
  arr.reduce((r, c) => (fn(c[k]) ? r[c[k]] = [...r[c[k]] || [], c] : null, r), {});

console.log(group(data, 'id'))     // grouping via `reduce`
console.log(groupBy(data, 'id'))   // same result if `fn` is omitted
console.log(groupBy(data, 'score', x => x > 2 )) // group with the iteratee

关于OP问题:

const data = [ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" } ]

const groupBy = (arr, k) => arr.reduce((r, c) => (r[c[k]] = [...r[c[k]] || [], c], r), {});
const groupWith = (arr, k, fn = () => true) => 
  arr.reduce((r, c) => (fn(c[k]) ? r[c[k]] = [...r[c[k]] || [], c] : null, r), {});

console.log(groupBy(data, 'Phase'))
console.log(groupWith(data, 'Value', x => x > 30 ))  // group by `Value` > 30

另一个ES6版本,它反转了分组并使用valuesas keyskeysas作为grouped values

const data = [{A: "1"}, {B: "10"}, {C: "10"}]

const groupKeys = arr => 
  arr.reduce((r,c) => (Object.keys(c).map(x => r[c[x]] = [...r[c[x]] || [], x]),r),{});

console.log(groupKeys(data))

注意:为简洁起见,为了简洁起见,仅以简短的形式(一行)发布了功能。您可以展开它们并添加其他错误检查等。

我会检查declarative-js, groupBy它似乎完全符合您的要求。也是:

  • 表现出色(性能基准
  • 用打字稿写的,所以包括所有打字。
  • 并不强制使用类似第三方数组的对象。
import { Reducers } from 'declarative-js';
import groupBy = Reducers.groupBy;
import Map = Reducers.Map;

const data = [
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
];

data.reduce(groupBy(element=> element.Step), Map());
data.reduce(groupBy('Step'), Map());
let groupbyKeys = function(arr, ...keys) {
  let keysFieldName = keys.join();
  return arr.map(ele => {
    let keysField = {};
    keysField[keysFieldName] = keys.reduce((keyValue, key) => {
      return keyValue + ele[key]
    }, "");
    return Object.assign({}, ele, keysField);
  }).reduce((groups, ele) => {
    (groups[ele[keysFieldName]] = groups[ele[keysFieldName]] || [])
      .push([ele].map(e => {
        if (keys.length > 1) {
          delete e[keysFieldName];
        }
        return e;
    })[0]);
    return groups;
  }, {});
};

console.log(groupbyKeys(array, 'Phase'));
console.log(groupbyKeys(array, 'Phase', 'Step'));
console.log(groupbyKeys(array, 'Phase', 'Step', 'Task'));

这是一个不会破坏null成员的ES6版本

function groupBy (arr, key) {
  return (arr || []).reduce((acc, x = {}) => ({
    ...acc,
    [x[key]]: [...acc[x[key]] || [], x]
  }), {})
}

具有分类功能

export const groupBy = function groupByArray(xs, key, sortKey) {
      return xs.reduce(function(rv, x) {
        let v = key instanceof Function ? key(x) : x[key];
        let el = rv.find(r => r && r.key === v);

        if (el) {
          el.values.push(x);
          el.values.sort(function(a, b) {
            return a[sortKey].toLowerCase().localeCompare(b[sortKey].toLowerCase());
          });
        } else {
          rv.push({ key: v, values: [x] });
        }

        return rv;
      }, []);
    };

样品:

var state = [
    {
      name: "Arkansas",
      population: "2.978M",
      flag:
  "https://upload.wikimedia.org/wikipedia/commons/9/9d/Flag_of_Arkansas.svg",
      category: "city"
    },{
      name: "Crkansas",
      population: "2.978M",
      flag:
        "https://upload.wikimedia.org/wikipedia/commons/9/9d/Flag_of_Arkansas.svg",
      category: "city"
    },
    {
      name: "Balifornia",
      population: "39.14M",
      flag:
        "https://upload.wikimedia.org/wikipedia/commons/0/01/Flag_of_California.svg",
      category: "city"
    },
    {
      name: "Florida",
      population: "20.27M",
      flag:
        "https://upload.wikimedia.org/wikipedia/commons/f/f7/Flag_of_Florida.svg",
      category: "airport"
    },
    {
      name: "Texas",
      population: "27.47M",
      flag:
        "https://upload.wikimedia.org/wikipedia/commons/f/f7/Flag_of_Texas.svg",
      category: "landmark"
    }
  ];
console.log(JSON.stringify(groupBy(state,'category','name')));
本文地址:http://javascript.askforanswer.com/duiduixiangshuzujinxingfenzudezuiyouxiaofangfa.html
文章标签: ,   ,   ,   ,  
版权声明:本文为原创文章,版权归 javascript 所有,欢迎分享本文,转载请保留出处!

文件下载

老薛主机终身7折优惠码boke112

上一篇:
下一篇:

评论已关闭!