javascript - ES6: How do I unravel inner arrays and flatten the JSON array? - Stack Overflow

admin管理员组

文章数量:1316645

Imagine that I have the following JSON array:

[
  {
    "team": "Colts",
    "players": [
      {
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [
      {
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
]

And I want to transform and flatten the JSON to be the following:

[
  {
    "name": "Andrew Luck",
    "position": "quarterback",
    "team": "Colts"
  },
  {
    "name": "Quenton Nelson",
    "position": "guard",
    "team": "Colts"
  },
  {
    "name": "Tom Brady",
    "position": "quarterback",
    "team": "Patriots"
  },
  {
    "name": "Shaq Mason",
    "position": "guard",
    "team": "Patriots"
  }
]

How would I do this with either ES6 or lodash syntax?

Imagine that I have the following JSON array:

[
  {
    "team": "Colts",
    "players": [
      {
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [
      {
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
]

And I want to transform and flatten the JSON to be the following:

[
  {
    "name": "Andrew Luck",
    "position": "quarterback",
    "team": "Colts"
  },
  {
    "name": "Quenton Nelson",
    "position": "guard",
    "team": "Colts"
  },
  {
    "name": "Tom Brady",
    "position": "quarterback",
    "team": "Patriots"
  },
  {
    "name": "Shaq Mason",
    "position": "guard",
    "team": "Patriots"
  }
]

How would I do this with either ES6 or lodash syntax?

• javascript
• json
• ecmascript-6
• lodash
• transformation

Share Improve this question Follow asked Mar 29, 2019 at 18:02 Jim G.Jim G. 15.4k2323 gold badges108108 silver badges176176 bronze badges

Add a ment  | 

7 Answers 7

Sorted by: Reset to default 5

With simple loops (ES2015):

const players = [];
for (const team of teams) {
  for (const player of team.players) {
    players.push(Object.assign({team: team.team}, player));
  }
}

You can use object spread instead of Object.assign if your environment supports it.

With Array#flatMap (will officially be part of ES2019, or use lodash):

const players = teams.flatMap(
  team => team.players.map(player => {...player, team: team.team})
);

Use Array#reduce method along with Array#map method.

let res = data.reduce((arr, { team, players }) => arr.concat(players.map( obj => ({...obj, team }))), []);

// or
let res = data.reduce((arr, { team, players }) => [...arr, ...players.map( obj => ({...obj, team }))], []);

// or
let res = data.reduce((arr, { team, players }) => (arr.push(...players.map( obj => ({...obj, team }))),arr), []);

var data = [{
    "team": "Colts",
    "players": [{
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [{
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
]

let res = data.reduce((arr, {
  team,
  players
}) => arr.concat(players.map(obj => ({ ...obj,
  team
}))), []);


// or
let res1 = data.reduce((arr, {
  team,
  players
}) => [...arr, ...players.map(obj => ({ ...obj,
  team
}))], []);

// or
let res2 = data.reduce((arr, {
  team,
  players
}) => (arr.push(...players.map(obj => ({ ...obj,
  team
}))), arr), []);


console.log(res, res1, res2)

You can use lodah's _.flatMap() to iterate the array and flatten the result. Internally use _.map() to iterate the players and add the team using object spread:

const arr = [{"team":"Colts","players":[{"name":"Andrew Luck","position":"quarterback"},{"name":"Quenton Nelson","position":"guard"}]},{"team":"Patriots","players":[{"name":"Tom Brady","position":"quarterback"},{"name":"Shaq Mason","position":"guard"}]}]

const result = _.flatMap(arr, ({ team, players }) => 
  _.map(players, o => ({ team, ...o }))
)

console.log(result)

<script src="https://cdnjs.cloudflare./ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

You can do the same with Array.flatMap() and Array.map():

const arr = [{"team":"Colts","players":[{"name":"Andrew Luck","position":"quarterback"},{"name":"Quenton Nelson","position":"guard"}]},{"team":"Patriots","players":[{"name":"Tom Brady","position":"quarterback"},{"name":"Shaq Mason","position":"guard"}]}]

const result = arr.flatMap(({ team, players }) => 
  players.map(o => ({ team, ...o }))
)

console.log(result)

<script src="https://cdnjs.cloudflare./ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

const data = [
  {
    "team": "Colts",
    "players": [
      {
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [
      {
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
]

const flatData = data.map(d => {
  const { team } = d
  const assignedPlayers = d.players.map(player => ({ team, ...player }))
  return assignedPlayers
}).flat()

console.log(flatData)

With ES6 (spread operator) along with reduce and concat:

const arr = [{
    "team": "Colts",
    "players": [{
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [{
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
]

console.log(arr.reduce((acc, obj) => {
  return acc.concat(...obj.players.map(player => {
    return Object.assign({
      team: obj.team
    }, player)
  }))
}, []));

This can be done simply using the following code! Check it!

var inputArray = [{"team":"Colts","players":[{"name":"Andrew Luck","position":"quarterback"},{"name":"Quenton Nelson","position":"guard"}]},{"team":"Patriots","players":[{"name":"Tom Brady","position":"quarterback"},{"name":"Shaq Mason","position":"guard"}]}]

var result = [];
inputArray.forEach(function(elem) {
  const players = elem.players;
  players.forEach(function(child) {
    const obj = {};
    obj["name"] = child.name;
    obj["position"] = child.position;
    obj["team"] = elem.team;
    result.push(obj);
  });
});

console.log(result);

.as-console-wrapper{max-height: 100% !important; top:0px;}

Here is another alternative with a bination of Array.reduce() and Array.forEach():

let input = [
  {
    "team": "Colts",
    "players": [
      {
        "name": "Andrew Luck",
        "position": "quarterback"
      },
      {
        "name": "Quenton Nelson",
        "position": "guard"
      }
    ]
  },
  {
    "team": "Patriots",
    "players": [
      {
        "name": "Tom Brady",
        "position": "quarterback"
      },
      {
        "name": "Shaq Mason",
        "position": "guard"
      }
    ]
  }
];

let output = input.reduce((acc, {team, players}) =>
{
    players.forEach(({name, position}) => acc.push({name, position, team}));
    return acc;
}, []);

console.log(output);

.as-console {background-color:black !important; color:lime;}
.as-console-wrapper {max-height:100% !important; top:0;}

本文标签： javascriptES6 How do I unravel inner arrays and flatten the JSON arrayStack Overflow