ES6：如何解开内部数组并展平 JSON 数组？答案

【问题标题】：ES6: How do I unravel inner arrays and flatten the JSON array?ES6：如何解开内部数组并展平 JSON 数组？
【发布时间】：2019-03-29 18:02:48
【问题描述】：

假设我有以下 JSON 数组：

[
  {
    "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"
      }
    ]
  }
]

我想将 JSON 转换并展平为以下内容：

[
  {
    "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"
  }
]

我将如何使用 ES6 或 lodash 语法来做到这一点？

【问题讨论】：

标签： javascript json ecmascript-6 lodash transformation

【解决方案1】：

使用简单循环（ES2015）：

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

如果您的环境支持，您可以使用对象传播而不是 Object.assign。

Array#flatMap（将正式成为 ES2019 的一部分，或使用 lodash）：

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

【讨论】：

【解决方案2】：

将Array#reduce 方法与Array#map 方法一起使用。

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)

【讨论】：

【解决方案3】：

您可以使用 lodah 的 _.flatMap() 来迭代数组并将结果展平。内部使用_.map() 迭代播放器并使用对象传播添加team：

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)

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"&gt;&lt;/script&gt;

Array.flatMap() 和 Array.map() 也可以这样做：

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)

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：

【解决方案4】：

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)

【讨论】：

【解决方案5】：

使用 ES6（扩展运算符）以及 reduce 和 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)
  }))
}, []));

【讨论】：

为将来的访问者澄清一下：reduce 在 ES6 之前就存在了。

【解决方案6】：

只需使用以下代码即可完成！检查一下！

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);

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【讨论】：

【解决方案7】：

这是Array.reduce() 和Array.forEach() 组合的另一种选择：

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);

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

【讨论】：