JavaScript 最近发布了一个方法 Object.groupBy，可以对可迭代对象中的元素进行分组。

语法：

Object.groupBy(items, callbackFn)

items

被分组的可迭代对象，如 Array。

callbackFn

对可迭代对象中的每个元素执行的函数。

举个例子，我们想要根据城市的首字符进行分组：

const cityList = [{ id: 1, name: "beijing" },{ id: 2, name: "shanghai" },{ id: 3, name: "guangzhou" },{ id: 4, name: "shenzhen" },{ id: 5, name: "hangzhou" },{ id: 6, name: "chengdu" },{ id: 7, name: "wuhan" },{ id: 8, name: "xian" },{ id: 9, name: "chongqing" },
];const result = Object.groupBy(cityList, (city) => city.name[0]);

返回结果：

{"b": [{"id": 1,"name": "beijing"}],"s": [{"id": 2,"name": "shanghai"},{"id": 4,"name": "shenzhen"}],"g": [{"id": 3,"name": "guangzhou"}],"h": [{"id": 5,"name": "hangzhou"}],"c": [{"id": 6,"name": "chengdu"},{"id": 9,"name": "chongqing"}],"w": [{"id": 7,"name": "wuhan"}],"x": [{"id": 8,"name": "xian"}]
}