将JavaScript中'_id'键具有相同值的所有对象组合在一起
假设我们有一个这样的对象数组-
const arr = [
{_id : "1", S : "2"},
{_id : "1", M : "4"},
{_id : "2", M : "1"},
{_id : "" , M : "1"},
{_id : "3", S : "3"}
];我们需要编写一个JavaScript函数，该函数接受一个这样的数组，并将所有具有相同“_id”键值的对象组合在一起。
因此，最终输出应如下所示：
const output = [
{_id : "1", M : "4", S : "2", Total: "6"},
{_id : "2", M : "1", S : "0", Total: "1"},
{_id : "6", M : "1", S : "0", Total: "1"},
{_id : "3", M : "0", S : "3", Total: "3"}
];示例
为此的代码将是-
const arr = [
{_id : "1", S : "2"},
{_id : "1", M : "4"},
{_id : "2", M : "1"},
{_id : "6" , M : "1"},
{_id : "3", S : "3"}
];
const pickAllConstraints = arr => {
let constraints = [];
arr.forEach(el => {
const keys = Object.keys(el);
constraints = [...constraints, ...keys];
});
return constraints.filter((el, ind) => el !== '_id' && ind === constraints.lastIndexOf(el));
};
const buildItem = (cons, el = {}, prev = {}) => {
const item = {};
let total = 0
cons.forEach(i => {
item[i] = (+el[i] || 0) + (+prev[i] || 0);
total += item[i];
});
item.total = total;
return item;
}
const buildCumulativeArray = arr => {
const constraints = pickAllConstraints(arr);
const map = {}, res = [];
arr.forEach(el => {
const { _id } = el;
if(map.hasOwnProperty(_id)){
res[map[_id] - 1] = {
_id, ...buildItem(constraints, el, res[map[_id] - 1])
};
}else{
map[_id] = res.push({
_id, ...buildItem(constraints, el)
});
}
});
return res;
};
console.log(buildCumulativeArray(arr));输出结果
控制台中的输出将是-
[
{ _id: '1', M: 4, S: 2, total: 6 },
{ _id: '2', M: 1, S: 0, total: 1 },
{ _id: '6', M: 1, S: 0, total: 1 },
{ _id: '3', M: 0, S: 3, total: 3 }
]