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Rumah > Soal Jawab > teks badan
P粉0293277112023-08-22 12:54:13
Menggunakan objek Peta ES6:
/**
* @description
* 接受一个类型为V的数组和一个分组函数，返回按照分组函数分组的数组的Map。
*
* @param list 类型为V的数组。
* @param keyGetter 一个函数，接受类型为V的数组作为输入，并返回类型为K的值。
* K通常是V的属性键。
*
* @returns 按照分组函数分组的数组的Map。
*/
//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;
}
// 使用示例
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"}]
const odd = Symbol();
const even = Symbol();
const numbers = [1,2,3,4,5,6,7];
const oddEven = groupBy(numbers, x => (x % 2 === 1 ? odd : even));
console.log(oddEven.get(odd)); // -> [1,3,5,7]
console.log(oddEven.get(even)); // -> [2,4,6]
Mengenai Peta: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
P粉5904283572023-08-22 11:08:27
Jika anda ingin mengelak daripada menggunakan perpustakaan luaran, anda boleh melaksanakan versi asli groupBy() seperti ini:
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"]}