您將如何使用 Javascript 更改值/添加到對象數組內的嵌套 object 數據？

Question

const beers = [
  {
    id: '100',
    name: 'stoneys'
  },
  {
    id: '200',
    name: 'budweiser'
  },

  {
    id: '300',
    name: 'miller'
  },

  {
    id: '400',
    name: 'corona'
  }
];

const people = [
  {
    name: 'steve',
    teams: [
      {
        name: 'pirates',
        beers: ['100']
      },
      {
        name: 'penguins',
        beers: ['300']
      }
    ]
  },
  {
    name: 'jim',
    teams: [
      {
        name: 'indians',
        beers: ['200']
      },
      {
        name: 'blue jackets',
        beers: ['100', '400']
      }
    ]
  }
];

let newPeople = people.map(fan => {
  fan.teams.map(team => {
    team.beers.map(beer => beers.filter(brand => brand.id === beer)[0])
  });
});

以上是我整理的一個示例，以最好地展示我的問題。 我無法理解為什么 object arrays 的嵌套映射 (.map()) 不允許我更改嵌套數據。 當我控制台日志結果時，我得到一個“[未定義，未定義]”或未更改的“人”數組。

我想返回與“人”相同的數組，除了用“啤酒”數組中的相應對象替換嵌套的“啤酒”數組（people.teams.beers []）。 下面的成功結果示例：

 {
    name: 'steve',
    teams: [
      {
        name: 'pirates',
        beers: [
          {
            id: '100',
            name: 'stoneys'
          }
        ]
      },
      {
        name: 'penguins',
        beers: [
          {
            id: '300',
            name: 'miller'
          }
        ]
      }
    ]
  }

Answer 1

Array.map需要一個 function ，它將單個數組元素作為參數並返回一個映射值。 在您的情況下，您沒有從映射函數返回任何值，因此您兩次未定義

 const beers = [ { id: '100', name: 'stoneys' }, { id: '200', name: 'budweiser' }, { id: '300', name: 'miller' }, { id: '400', name: 'corona' } ]; const people = [ { name: 'steve', teams: [ { name: 'pirates', beers: ['100'] }, { name: 'penguins', beers: ['300'] } ] }, { name: 'jim', teams: [ { name: 'indians', beers: ['200'] }, { name: 'blue jackets', beers: ['100', '400'] } ] } ]; let newPeople = people.map(fan => { let teams = fan.teams.map(team => { let beer = team.beers.map(beer => beers.filter(brand => brand.id === beer)[0]); return { name: team.name, beers: beer } }); return { name: fan.name, teams: teams } }); console.log(newPeople);