按javascript中的属性对对象进行分组

Question

如何转换这个:

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

进入这个:

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

使用javascript或下划线

Answer 1

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();

Answer 2

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));

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

幸得@ErikE为提高/降低我的原代码,以帮助冗余我不得不:)

Answer 3

这是@ Ian的答案略有不同但更通用的版本

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'));

你可以在这里找到一个jsfiddle