JavaScript通过两个属性将JSON对象分组并计数
假设我们有一个像这样的对象数组-
const arr = [
{"location":"Kirrawee","identity_long":"student"},
{"location":"Kirrawee","identity_long":"visitor"},
{"location":"Kirrawee","identity_long":"visitor"},
{"location":"Kirrawee","identity_long":"worker"},
{"location":"Sutherland","identity_long":"student"},
{"location":"Sutherland","identity_long":"resident"},
{"location":"Sutherland","identity_long":"worker"},
{"location":"Sutherland","identity_long":"resident"},
{"location":"Miranda","identity_long":"resident"},
{"location":"Miranda","identity_long":"worker"},
{"location":"Miranda","identity_long":"student"},
{"location":"Miranda","identity_long":""},
{"location":"Miranda","identity_long":"worker"},
{"location":"Miranda","identity_long":"resident"}
];我们需要编写一个JavaScript函数，该函数接受一个这样的对象数组。函数应准备一个新的对象数组，其中所有（相同的）对象都基于location属性分组在一起。
并且应该为对象分配一个count属性，该属性包含它在对象原始数组中出现的次数。
因此，对于上述数组，输出应类似于-
const output = [
{"location":"Kirrawee","identity":"student","count":1},
{"location":"Kirrawee","identity":"visitor","count":2},
{"location":"Kirrawee","identity":"worker","count":1},
{"location":"Sutherland","identity":"student","count":1},
{"location":"Sutherland","identity":"resident","count":2},
{"location":"Sutherland","identity":"worker","count":1},
{"location":"Miranda","identity":"resident","count":2},
{"location":"Miranda","identity":"worker","count":2},
{"location":"Miranda","identity":"student","count":1}
];示例
为此的代码将是-
const arr = [
{"location":"Kirrawee","identity_long":"student"},
{"location":"Kirrawee","identity_long":"visitor"},
{"location":"Kirrawee","identity_long":"visitor"},
{"location":"Kirrawee","identity_long":"worker"},
{"location":"Sutherland","identity_long":"student"},
{"location":"Sutherland","identity_long":"resident"},
{"location":"Sutherland","identity_long":"worker"},
{"location":"Sutherland","identity_long":"resident"},
{"location":"Miranda","identity_long":"resident"},
{"location":"Miranda","identity_long":"worker"},
{"location":"Miranda","identity_long":"student"},
{"location":"Miranda","identity_long":""},
{"location":"Miranda","identity_long":"worker"},
{"location":"Miranda","identity_long":"resident"}
];
const groupArray = (arr = []) => {
//创建映射
let map = new Map() for (let i = 0; i < arr.length; i++) {
const s = JSON.stringify(arr[i]);
if (!map.has(s)) {
map.set(s, {
location: arr[i].location,
identity: arr[i].identity_long,
count: 1,
});
} else {
map.get(s).count++;
}
}
const res = Array.from(map.values())
return res;
};
console.log(groupArray(arr));输出结果
控制台中的输出将是-
[
{ location: 'Kirrawee', identity: 'student', count: 1 },
{ location: 'Kirrawee', identity: 'visitor', count: 2 },
{ location: 'Kirrawee', identity: 'worker', count: 1 },
{ location: 'Sutherland', identity: 'student', count: 1 },
{ location: 'Sutherland', identity: 'resident', count: 2 },
{ location: 'Sutherland', identity: 'worker', count: 1 },
{ location: 'Miranda', identity: 'resident', count: 2 },
{ location: 'Miranda', identity: 'worker', count: 2 },
{ location: 'Miranda', identity: 'student', count: 1 },
{ location: 'Miranda', identity: '', count: 1 }
]