有人知道一种方法(lodash如果可能的话)通过对象键分组对象数组,然后根据分组创建一个新的对象数组吗?例如,我有一个汽车对象数组:
const cars = [
{
'make': 'audi',
'model': 'r8',
'year': '2012'
}, {
'make': 'audi',
'model': 'rs5',
'year': '2013'
}, {
'make': 'ford',
'model': 'mustang',
'year': '2012'
}, {
'make': 'ford',
'model': 'fusion',
'year': '2015'
}, {
'make': 'kia',
'model': 'optima',
'year': '2012'
},
];
我想创建一个新的汽车对象数组,由make分组:
const cars = {
'audi': [
{
'model': 'r8',
'year': '2012'
}, {
'model': 'rs5',
'year': '2013'
},
],
'ford': [
{
'model': 'mustang',
'year': '2012'
}, {
'model': 'fusion',
'year': '2015'
}
],
'kia': [
{
'model': 'optima',
'year': '2012'
}
]
}
提莫的答案是我会怎么做。简单的_。groupBy,并允许在分组结构中的对象中有一些重复。
然而,OP还要求删除重复的make键。如果你想从头到尾:
var grouped = _.mapValues(_.groupBy(cars, 'make'),
clist => clist.map(car => _.omit(car, 'make')));
console.log(grouped);
收益率:
{ audi:
[ { model: 'r8', year: '2012' },
{ model: 'rs5', year: '2013' } ],
ford:
[ { model: 'mustang', year: '2012' },
{ model: 'fusion', year: '2015' } ],
kia:
[ { model: 'optima', year: '2012' } ]
}
如果你想使用Underscore.js来实现这个功能,请注意它的_. js版本。mapValues被称为_.mapObject。
Var汽车= [{
:“奥迪”,
模型:“r8”,
:“2012”
},{
:“奥迪”,
模型:“生活费”,
:“2013”
},{
:“福特”,
模型:“野马”,
:“2012”
},{
:“福特”,
模型:“融合”,
:“2015”
},{
:“克钦独立军”,
模型:“最佳状态”,
:“2012”
})。Reduce ((r, car) => {
const {
模型中,
一年,
使
} =汽车;
R [make] =[…]R [make] || [], {
模型中,
一年
});
返回r;
}, {});
console.log(汽车);
const reGroup = (list, key) => {
const newGroup = {};
list.forEach(item => {
const newItem = Object.assign({}, item);
delete newItem[key];
newGroup[item[key]] = newGroup[item[key]] || [];
newGroup[item[key]].push(newItem);
});
return newGroup;
};
const animals = [
{
type: 'dog',
breed: 'puddle'
},
{
type: 'dog',
breed: 'labradoodle'
},
{
type: 'cat',
breed: 'siamese'
},
{
type: 'dog',
breed: 'french bulldog'
},
{
type: 'cat',
breed: 'mud'
}
];
console.log(reGroup(animals, 'type'));
const cars = [
{
'make': 'audi',
'model': 'r8',
'year': '2012'
}, {
'make': 'audi',
'model': 'rs5',
'year': '2013'
}, {
'make': 'ford',
'model': 'mustang',
'year': '2012'
}, {
'make': 'ford',
'model': 'fusion',
'year': '2015'
}, {
'make': 'kia',
'model': 'optima',
'year': '2012'
},
];
console.log(reGroup(cars, 'make'));
同意除非经常使用这些库,否则不需要外部库。虽然有类似的解决方案,但我发现其中一些很难遵循。如果您试图理解正在发生的事情,这里有一个带有注释的解决方案的要点。
const cars = [{
'make': 'audi',
'model': 'r8',
'year': '2012'
}, {
'make': 'audi',
'model': 'rs5',
'year': '2013'
}, {
'make': 'ford',
'model': 'mustang',
'year': '2012'
}, {
'make': 'ford',
'model': 'fusion',
'year': '2015'
}, {
'make': 'kia',
'model': 'optima',
'year': '2012'
}, ];
/**
* Groups an array of objects by a key an returns an object or array grouped by provided key.
* @param array - array to group objects by key.
* @param key - key to group array objects by.
* @param removeKey - remove the key and it's value from the resulting object.
* @param outputType - type of structure the output should be contained in.
*/
const groupBy = (
inputArray,
key,
removeKey = false,
outputType = {},
) => {
return inputArray.reduce(
(previous, current) => {
// Get the current value that matches the input key and remove the key value for it.
const {
[key]: keyValue
} = current;
// remove the key if option is set
removeKey && keyValue && delete current[key];
// If there is already an array for the user provided key use it else default to an empty array.
const {
[keyValue]: reducedValue = []
} = previous;
// Create a new object and return that merges the previous with the current object
return Object.assign(previous, {
[keyValue]: reducedValue.concat(current)
});
},
// Replace the object here to an array to change output object to an array
outputType,
);
};
console.log(groupBy(cars, 'make', true))
使用lodash/fp,你可以使用_.flow()创建一个函数,它首先按键分组,然后映射每个组,并从每个项中省略一个键:
const { flow, groupBy, mapValues, map, omit } = _;
const groupAndOmitBy = key => flow(
groupBy(key),
mapValues(map(omit(key)))
);
const cars = [{ make: 'audi', model: 'r8', year: '2012' }, { make: 'audi', model: 'rs5', year: '2013' }, { make: 'ford', model: 'mustang', year: '2012' }, { make: 'ford', model: 'fusion', year: '2015' }, { make: 'kia', model: 'optima', year: '2012' }];
const groupAndOmitMake = groupAndOmitBy('make');
const result = groupAndOmitMake(cars);
console.log(result);
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