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法學對陣列進行分組和統計專案，根據 JavaScript 中的分組建立一個新陣列
假設我們有一個這樣的物件陣列 -
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" }
];我們需要寫一個 JavaScript 函式來輸入一個這樣的陣列。該函式應當準備一個新的物件陣列，根據物件的“area”屬性對資料進行分組。
該函式還應統計特定區域的唯一使用者數量。
因此，對於上述陣列，輸出應如下所示 -
const output = [
{
"region": "Africa",
"count": 2
},
{
"region": "Europe",
"count": 2
},
{
"region": "Asia",
"count": 2
}
];示例
程式碼如下 -
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));輸出
控制檯中的輸出將為 -
[
{ region: 'Africa', count: 2 },
{ region: 'Europe', count: 2 },
{ region: 'Asia', count: 2 }
]
更新於： 2020 年 11 月 24 日
196 次瀏覽
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