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'
}
]
}
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))
您正在寻找_.groupBy()。
如果需要，从对象中删除分组的属性应该很简单:
Const cars = [{
“做”:“奥迪”,
“模型”:“r8”,
“年”:“2012”
},{
“做”:“奥迪”,
“模型”:“生活费”,
“年”:“2013”
},{
“做”:“福特”,
“模型”:“野马”,
“年”:“2012”
},{
“做”:“福特”,
“模型”:“融合”,
“年”:“2015”
},{
“做”:“克钦独立军”,
“模型”:“最佳状态”,
“年”:“2012”
});
Const分组= _。groupBy(cars, car => car.make);
console.log(分组);
< script src = " https://cdn.jsdelivr.net/lodash/4.17.2/lodash.min.js " > < /脚本>
Prototype version using ES6 as well.
Basically this uses the reduce function to pass in an accumulator and current item, which then uses this to build your "grouped" arrays based on the passed in key. the inner part of the reduce may look complicated but essentially it is testing to see if the key of the passed in object exists and if it doesn't then create an empty array and append the current item to that newly created array otherwise using the spread operator pass in all the objects of the current key array and append current item. Hope this helps someone!.
Array.prototype.groupBy = function(k) {
return this.reduce((acc, item) => ((acc[item[k]] = [...(acc[item[k]] || []), item]), acc),{});
};
const projs = [
{
project: "A",
timeTake: 2,
desc: "this is a description"
},
{
project: "B",
timeTake: 4,
desc: "this is a description"
},
{
project: "A",
timeTake: 12,
desc: "this is a description"
},
{
project: "B",
timeTake: 45,
desc: "this is a description"
}
];
console.log(projs.groupBy("project"));
创建一个可以重用的方法
Array.prototype.groupBy = function(prop) {
return this.reduce(function(groups, item) {
const val = item[prop]
groups[val] = groups[val] || []
groups[val].push(item)
return groups
}, {})
};
下面你可以根据任何标准进行分组
const groupByMake = cars.groupBy('make');
console.log(groupByMake);
var 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'
},
];
//re-usable method
Array.prototype.groupBy = function(prop) {
return this.reduce(function(groups, item) {
const val = item[prop]
groups[val] = groups[val] || []
groups[val].push(item)
return groups
}, {})
};
// initiate your groupBy. Notice the recordset Cars and the field Make....
const groupByMake = cars.groupBy('make');
console.log(groupByMake);
//At this point we have objects. You can use Object.keys to return an array
