Reduce array of objects by user_id and sum certain values

问题

I have an array of objects that looks like this:

"data": [
{ "workout_id": 1, "user_id": 1, "shotLocation": 27, "shotAttempts": 20,"shotsMade": 19, "id": 1 },
{ "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 2 },
{ "workout_id": 2, "user_id": 1, "shotLocation": 10, "shotAttempts": 10, "shotsMade": 7, "id": 3 },
{ "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 29, "id": 4 },
{ "workout_id": 3, "user_id": 5, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 5 },
{ "workout_id": 4, "user_id": 6, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 15, "id": 6 },
{ "workout_id": 4, "user_id": 6, "shotLocation": 2, "shotAttempts": 20, "shotsMade": 14, "id": 7 }
]

I would like to create a new array of objects where I

reduce the user_ids to each unique user
then calculate the total shotAttempts and shotsMade for each user

like this:

"dataTotals" : [
{"id": 1, "user_id": 1, "shotAttempts": 90, "shotsMade": 64}
{"id": 2, "user_id": 5, "shotAttempts": 10, "shotsMade": 9}
{"id": 3, "user_id": 6, "shotAttempts": 50, "shotsMade": 29}

I plan on iterating over this new array of objects with a .map function to populate a leaderboard as more users record their data.

I've tried several different ways to achieve this based on what I've read about the .map and .reduce methods, as well as searching here and found something that's close, but it returns an object as indicated below.

like this:

// create new object to store results in
let newObj = {};
// loop through user objects
this.state.shotlogs.forEach(function(shotlog){
// check if user_id  has already been added to newObj
if(!newObj[shotlog.user_id]){
// If it is the first time seeing this user_id
// we need to add shots attempted and shots made to prevent errors
newObj[shotlog.user_id] = {};
newObj[shotlog.user_id]['user_id'] = shotlog.user_id;
newObj[shotlog.user_id]['shotAttempts'] = 0;
newObj[shotlog.user_id]['shotsMade'] = 0;
}
// add shots attempted and made to newObj for this user
newObj[shotlog.user_id]['shotAttempts'] += shotlog.shotAttempts
newObj[shotlog.user_id]['shotsMade'] += shotlog.shotsMade
})

but this returns an object that looks like this and not an array of objects like above:

{
1: {user_id: 1, shotAttempts: 70, shotsMade: 64}
5: {user_id: 5, shotAttempts: 10, shotsMade: 9}
6: {user_id: 6, shotAttempts: 50, shotsMade: 29}
}

Any help for this new coder is greatly appreciated!!

回答1:

You can use Array.reduce, Object.values with ES6 destructuring and solve this in a concise manner:

const data = [{ "workout_id": 1, "user_id": 1, "shotLocation": 27, "shotAttempts": 20, "shotsMade": 19, "id": 1 }, { "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 2 }, { "workout_id": 2, "user_id": 1, "shotLocation": 10, "shotAttempts": 10, "shotsMade": 7, "id": 3 }, { "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 29, "id": 4 }, { "workout_id": 3, "user_id": 5, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 5 }, { "workout_id": 4, "user_id": 6, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 15, "id": 6 }, { "workout_id": 4, "user_id": 6, "shotLocation": 2, "shotAttempts": 20, "shotsMade": 14, "id": 7 } ]

const result = data.reduce((r,{workout_id, user_id, shotAttempts, shotsMade}) => {
 r[user_id] = r[user_id] || {id: workout_id, user_id, shotAttempts: 0, shotsMade: 0}
 r[user_id].shotAttempts += shotAttempts
 r[user_id].shotsMade += shotsMade
 return r
}, {})

console.log(Object.values(result))

回答2:

You can use Array.prototype.reduce()

Code:

const data = [{ "workout_id": 1, "user_id": 1, "shotLocation": 27, "shotAttempts": 20,"shotsMade": 19, "id": 1 },{ "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 2 },{ "workout_id": 2, "user_id": 1, "shotLocation": 10, "shotAttempts": 10, "shotsMade": 7, "id": 3 },{ "workout_id": 2, "user_id": 1, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 29, "id": 4 },{ "workout_id": 3, "user_id": 5, "shotLocation": 1, "shotAttempts": 10, "shotsMade": 9, "id": 5 },{ "workout_id": 4, "user_id": 6, "shotLocation": 1, "shotAttempts": 30, "shotsMade": 15, "id": 6 },{ "workout_id": 4, "user_id": 6, "shotLocation": 2, "shotAttempts": 20, "shotsMade": 14, "id": 7 }];
const dataTotals = Object.values(data.reduce((a, c) => {
  if (!a[c.user_id]) {
    a[c.user_id] = {
      id: c.workout_id,
      user_id: c.user_id,
      shotAttempts: c.shotAttempts,
      shotsMade: c.shotsMade
    };
  } else {  
    a[c.user_id].shotAttempts += c.shotAttempts;
    a[c.user_id].shotsMade += c.shotsMade;
  }
  return a;
}, {}));

console.log(dataTotals);

回答3:

const data = [
  { workout_id: 1, user_id: 1, shotLocation: 27, shotAttempts: 20, shotsMade: 19, id: 1 },
  { workout_id: 2, user_id: 1, shotLocation: 1, shotAttempts: 10, shotsMade: 9, id: 2 },
  { workout_id: 2, user_id: 1, shotLocation: 10, shotAttempts: 10, shotsMade: 7, id: 3 },
  { workout_id: 2, user_id: 1, shotLocation: 1, shotAttempts: 30, shotsMade: 29, id: 4 },
  { workout_id: 3, user_id: 5, shotLocation: 1, shotAttempts: 10, shotsMade: 9, id: 5 },
  { workout_id: 4, user_id: 6, shotLocation: 1, shotAttempts: 30, shotsMade: 15, id: 6 },
  { workout_id: 4, user_id: 6, shotLocation: 2, shotAttempts: 20, shotsMade: 14, id: 7 }
];

const shooters = data.reduce(
  (results, current) => ({
    ...results,
    [current.user_id]: {
      user_id: current.user_id,
      shotAttempts: current.shotAttempts + (results[current.user_id] ? results[current.user_id].shotAttempts : 0),
      shotsMade: current.shotsMade + (results[current.user_id] ? results[current.user_id].shotsMade : 0)
    }
  }),
  {}
);

console.log(shooters);

来源：https://stackoverflow.com/questions/53826570/reduce-array-of-objects-by-user-id-and-sum-certain-values

标签

javascript

arrays

object

reduce