javascript 在javascript中按属性对对象进行分组

Group objects by property in javascript

提问by Anurag

How to convert this:

如何转换这个：

[
    {food: 'apple', type: 'fruit'},
    {food: 'potato', type: 'vegetable'},
    {food: 'banana', type: 'fruit'},
]

into this:

进入这个：

[
    {type: 'fruit', foods: ['apple', 'banana']},
    {type: 'vegetable', foods: ['potato']}
]

using javascript or underscore

使用 javascript 或下划线

回答by Anurag

Assuming the original list is contained in a variable named list:

假设原始列表包含在名为 的变量中list：

_
.chain(list)
.groupBy('type')
.map(function(value, key) {
    return {
        type: key,
        foods: _.pluck(value, 'food')
    }
})
.value();

回答by Ian

Without using underscore:

不使用下划线：

var origArr = [
    {food: 'apple', type: 'fruit'},
    {food: 'potato', type: 'vegetable'},
    {food: 'banana', type: 'fruit'}
];

/*[
    {type: 'fruit', foods: ['apple', 'banana']},
    {type: 'vegetable', foods: ['potato']}
]*/

function transformArr(orig) {
    var newArr = [],
        types = {},
        i, j, cur;
    for (i = 0, j = orig.length; i < j; i++) {
        cur = orig[i];
        if (!(cur.type in types)) {
            types[cur.type] = {type: cur.type, foods: []};
            newArr.push(types[cur.type]);
        }
        types[cur.type].foods.push(cur.food);
    }
    return newArr;
}

console.log(transformArr(origArr));

DEMO:http://jsfiddle.net/ErikE/nSLua/3/

演示：http : //jsfiddle.net/ErikE/nSLua/3/

Credit goes to @ErikEfor improving/reducing my original code to help with redundancy I had :)

幸得@ErikE为提高/降低我的原代码，以帮助冗余我不得不:)

回答by Obi

Here is a slightly different but more generic version of @Ian's answer

这是@Ian 答案的一个稍微不同但更通用的版本

Caveat: the result is slightly different from the OP requirement, but others like me who stumble on this question might benefit from a more generic answer IMHO

警告：结果与 OP 要求略有不同，但像我这样偶然发现这个问题的其他人可能会受益于更通用的答案恕我直言

var origArr = [
   {food: 'apple', type: 'fruit'},
   {food: 'potato', type: 'vegetable'},
   {food: 'banana', type: 'fruit'}
];

function groupBy(arr, key) {
        var newArr = [],
            types = {},
            newItem, i, j, cur;
        for (i = 0, j = arr.length; i < j; i++) {
            cur = arr[i];
            if (!(cur[key] in types)) {
                types[cur[key]] = { type: cur[key], data: [] };
                newArr.push(types[cur[key]]);
            }
            types[cur[key]].data.push(cur);
        }
        return newArr;
}

console.log(groupBy(origArr, 'type'));

You can find a jsfiddle here

你可以在这里找到一个jsfiddle

回答by Ori Drori

An ES6 solution to this old question:

这个老问题的 ES6 解决方案：

Iterate using Array#reduce, and collect the items by group into a Map. Use spread to convert the Map#valuesback into array:

迭代 using Array#reduce，并按组将项目收集到Map. 使用 spread 将Map#values返回转换为数组：

const data = [
    {food: 'apple', type: 'fruit'},
    {food: 'potato', type: 'vegetable'},
    {food: 'banana', type: 'fruit'},
];

const result = [...data.reduce((hash, { food, type }) => {
  const current = hash.get(type) || { type, foods: [] };
  
  current.foods.push({ food });
  
  return hash.set(type, current);
}, new Map).values()];

console.log(result);

回答by jcreamer898

var foods = [
    {food: 'apple', type: 'fruit'},
    {food: 'potato', type: 'vegetable'},
    {food: 'banana', type: 'fruit'}
];

var newFoods = _.chain( foods ).reduce(function( memo, food ) {
  memo[ food.type ] = memo[ food.type ] || [];
  memo[ food.type ].push( food.food );
  return memo;
}, {}).map(function( foods, type ) {
    return {
        type: type,
        foods: foods
    };
}).value();

http://jsbin.com/etaxih/2/edit

http://jsbin.com/etaxh/2/edit

回答by agershun

You can group array of objects by one of fields with Alasql library. This example compact arrays exactly as in your example:

您可以使用 Alasql 库按字段之一对对象数组进行分组。此示例紧凑数组与您的示例完全相同：

var res = alasql('SELECT type, ARRAY(food) AS foods FROM ? GROUP BY type',[food]);

Try this example at jsFiddle.

在 jsFiddle试试这个例子。

回答by Justin Levine

You could also use other ES6 Features such as:

您还可以使用其他 ES6 功能，例如：

function groupArray(arr, groupBy, keepProperty) {
        let rArr = [], i;
        arr.forEach(item => {
            if((i = rArr.findIndex(obj => obj[groupBy] === item[groupBy])) !== -1)
                rArr[i][`${keepProperty}s`].push(item[keepProperty]);
            else rArr.push({
                [groupBy]: item[groupBy],
                [`${keepProperty}s`]: [item[keepProperty]]
            });
        });
        return rArr;
    }

    groupArray(yourArray, 'type', 'food');