count 元素基于匹配 id JavaScript

Question

var data = [{
id: '1',
status: 'pending'
}, {
id: '2',
status: 'delivered'
}, {
id: '2',
status: 'pending'
}, {
id: '1',
status: 'shipped'
}, {
id: '1',
status: 'pending'
}, {
id: '2',
status: 'delivered'
}, {
id: '2',
status: 'shipped'
}]

output: [{
id: 1,
order: {
pending: 2,
shipped: 1
},
id: 2,
order: {
pending: 1,
delivered: 2,
shipped: 1
}
}]

Answer 1

使用Array reduce和find执行此操作的一种方法。

var ret = data.reduce(function(o, v) {
//change id to Number
var idNum = Number(v.id);
var ele = o.find(function(e, i) {
return idNum === e.id;
});
if (!ele) {
//ID is not there in our output, let's create it
ele = {
id: idNum,
order: {}
};
o.push(ele);
}
//update order status
//if it's empty start with zero and increase it
ele.order[v.status] = (ele.order[v.status] || 0) + 1;
return o;
}, []);
console.log(JSON.stringify(ret));

Answer 2

使用Array#reduce创建对象，以 id 作为键和要转换的Object#values()

var data = [{
id: '1',
status: 'pending'
}, {
id: '2',
status: 'delivered'
}, {
id: '2',
status: 'pending'
}, {
id: '1',
status: 'shipped'
}, {
id: '1',
status: 'pending'
}, {
id: '2',
status: 'delivered'
}, {
id: '2',
status: 'shipped'
}]
let res = Object.values(
data.reduce((a, c) => {
if (!a[c.id]) {
a[c.id] = {id: c.id, order: {pending:0, shipped:0, delivered:0}};
}
a[c.id].order[c.status] ++;
return a
}, {})
);
console.log(res)

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