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法学对数组进行分组和统计项目，根据 JavaScript 中的分组创建一个新数组
假设我们有一个这样的对象数组 -
const arr = [
{ region: "Africa", fruit: "Orange", user: "Gary" },
{ region: "Africa", fruit: "Apple", user: "Steve" },
{ region: "Europe", fruit: "Orange", user: "John" },
{ region: "Europe", fruit: "Apple", user: "bob" },
{ region: "Asia", fruit: "Orange", user: "Ian" },
{ region: "Asia", fruit: "Apple", user: "Angelo" },
{ region: "Africa", fruit: "Orange", user: "Gary" }
];我们需要写一个 JavaScript 函数来输入一个这样的数组。该函数应当准备一个新的对象数组，根据对象的“area”属性对数据进行分组。
该函数还应统计特定区域的唯一用户数量。
因此，对于上述数组，输出应如下所示 -
const output = [
{
"region": "Africa",
"count": 2
},
{
"region": "Europe",
"count": 2
},
{
"region": "Asia",
"count": 2
}
];示例
代码如下 -
const arr = [
{ region: "Africa", fruit: "Orange", user: "Gary" },
{ region: "Africa", fruit: "Apple", user: "Steve" },
{ region: "Europe", fruit: "Orange", user: "John" },
{ region: "Europe", fruit: "Apple", user: "bob" },
{ region: "Asia", fruit: "Orange", user: "Ian" },
{ region: "Asia", fruit: "Apple", user: "Angelo" },
{ region: "Africa", fruit: "Orange", user: "Gary" }
];
const groupByArea = (arr = []) => {
const res = [];
arr.forEach(el => {
let key = [el.region, el.user].join('|');
if (!this[el.region]) {
this[el.region] = { region: el.region, count: 0 };
res.push(this[el.region]);
};
if (!this[key]) {
this[key] = true;
this[el.region].count++;
};
}, Object.create(null));
return res;
}
console.log(groupByArea(arr));输出
控制台中的输出将为 -
[
{ region: 'Africa', count: 2 },
{ region: 'Europe', count: 2 },
{ region: 'Asia', count: 2 }
]
更新于： 2020 年 11 月 24 日
196 次浏览
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