Question

以一个对象数组为例，每个对象都具有某些数组属性，例如versions，targets。我想为每个version和target取消对象分组。

const myArray = [
  { 'name': 'a', versions: [1, 2], targets: ['server1', 'server2']},
  { 'name': 'b', versions: [], targets: ['server1', 'server2', 'server3']},
  { 'name': 'c', versions: [1], targets: []}
]

上面myArray的期望输出为：

[
  { 'name': 'a', version: 1,         target: 'server1'},
  { 'name': 'a', version: 1,         target: 'server2'},
  { 'name': 'a', version: 2,         target: 'server1'},
  { 'name': 'a', version: 2,         target: 'server2'},
  { 'name': 'b', version: undefined, target: 'server1'},
  { 'name': 'b', version: undefined, target: 'server2'},
  { 'name': 'b', version: undefined, target: 'server3'},
  { 'name': 'c', version: 1,         target: undefined},
]

我考虑使用嵌套的for / forEach循环，但是几乎可以肯定的是，必须有一种更精确，更合理的方法来实现内置的es6函数。这就是我要的。

Answer 1

您可以使用fmap：

.flatMap

或者具有更大的尺寸，生成器将变得非常有用：

  const notEmpty = arr => arr.length ? arr : [undefined];

  myArray.flatMap(({ name, versions, targets }) => notEmpty(versions).flatMap(version => notEmpty(targets).map(target => ({ name, version, target }))));

Answer 2

您可以使用reduce方法：

const result = myArray.reduce((a, {name, versions, targets}) => {
  versions.forEach((el, ind) => {
      a.push({name, version: versions[ind], target: targets[ind]})
  });
  targets.forEach((el, ind) => {
      a.push({name, version: versions[ind], target: targets[ind]})
  });  
  return a;    
}, []);

一个例子：

const myArray = [
  { 'name': 'a', versions: [1, 2], targets: ['server1', 'server2']},
  { 'name': 'b', versions: [], targets: ['server1', 'server2', 'server3']},
  { 'name': 'c', versions: [1], targets: []}
]


const result = myArray.reduce((a, {name, versions, targets}) => {
  versions.forEach((el, ind) => {
      a.push({name, version: versions[ind], target: targets[ind]})
  });
  targets.forEach((el, ind) => {
      a.push({name, version: versions[ind], target: targets[ind]})
 });  
  return a;
}, []);

console.log(result);

Answer 3

const myArray = [
  { 'name': 'a', versions: [1, 2], targets: ['server1', 'server2'] },
  { 'name': 'b', versions: [], targets: ['server1', 'server2', 'server3'] },
  { 'name': 'c', versions: [1], targets: [] }
]

const reducer = (acc, current) => {
  const { name, versions, targets } = current;
  for (let i = 0; i < versions.length; i++) {
    acc.push({ name, version: versions[i], target: targets[i] })
  }

  for (let i = 0; i < targets.length; i++) {
    acc.push({ name, version: versions[i], target: targets[i] })
  }

  return acc;
}

const ungroup = array => array.reduce(reducer, [])

console.log(ungroup(myArray))

如何基于Javascript中的多个数组属性对对象数组进行分组

3 个答案: