通过 reduce 修改对象数组

Question

I have an array like ->

[{amount: 5000, date: "2020-04", user: "Bill Gates"}, {amount: 5000, date: "2020-04", user: "Jon Jones"}, {amount: 5000, date: "2020-05", user: "Jon Jones"}, {amount: 5000, date: "2020-05", user: "Bill Gates"}, ...]

And I want to modify it to ->

[{user: "Bill Gates", data: [{amount: 5000, date: "2020-04"}, {amount: 5000, date: "2020-05"}]}, {user: "Jon Jones", data: [{amount: 5000, date: "2020-04"}, {amount: 5000, date: "2020-05"}]}, ....]

I write reduce function ->

let reduced = array.reduce((sells, {user, date, amount}) => ({
    ...sells,
    user: user,
    data: [{date: date, amount: amount}],
}),{});

but it returns just one item of array. How can I return all of them?

Answer 1

You can search for the user using Array.prototype.find if found that means it is already processed and you can push the data object in the existing array else create a new object and insert it in the accumulator:

 const data = [{amount: 5000, date: "2020-04", user: "Bill Gates"}, {amount: 5000, date: "2020-04", user: "Jon Jones"}, {amount: 5000, date: "2020-05", user: "Jon Jones"}, {amount: 5000, date: "2020-05", user: "Bill Gates"}]; const result = data.reduce((sells, {user, date, amount}) => { let match = sells.find(e => e.user === user); if(match){ match.data.push({amount, date}); }else{ match = {user, data: [{amount, date}]}; sells.push(match); } return sells; }, []); console.log(result);

Answer 2

input.reduce((acc, {user, amount, date}) => {
    const userToExtend = acc.find(u => u.user === user)
    if(userToExtend) userToExtend.data.push[{amount, date}]
    else acc.push({user, data: [{amount, date}]});
    return acc
}, []);