javascript - 推送到 map / promise 内的新数组

Question

这是我当前设置的简化版本。

运行此代码时，您会注意到修改 changes 数组也会操作原始 referrals 数组。这是因为我正在 pushing 到 map 函数内的 changes 数组吗？如何在不修改 referrals 数组的情况下修改 changes 数组？

var referrals = [
  {
    id: 1,
    name: 'John',
    change: true
  },
  {
    id: 2,
    name: 'Sally',
    change: false
  },
  {
    id: 3,
    name: 'Kim',
    change: true
  }
];

var changes = [];

var process = referrals.map(function(referral) {
  return new Promise(function(resolve, reject) {
    if (referral.change) {
      changes.push(referral);
    }
    resolve();
  });
});

Promise.all(process).then(function() {
  console.log('referrals before:', referrals);
  changes = changes.map(function(change) {
    change.change_id = change.id;
    delete change.id;
    return change;
  });

  console.log('changes:', changes);
  console.log('referrals after:', referrals);
});

Answer 1

您只需要创建内部对象的深拷贝，可以使用 lodash deepClone 或 spread 运算符来完成。

类似的事情:

var referrals = [
{
  id: 1,
  name: 'John',
  change: true
},
{
  id: 2,
  name: 'Sally',
  change: false
},
{
  id: 3,
  name: 'Kim',
  change: true
}
];

var changes = [];

var process = referrals.map(function(referral) {
  return new Promise(function(resolve, reject) {
    if (referral.change) {
      changes.push({...referral}); // You will create a copy here.
    }
    resolve();
  });
});

Promise.all(process).then(function() {
  console.log('referrals before:', referrals);
  changes = changes.map(function(change) {
  change.change_id = change.id;
  delete change.id;
  return change;
});

console.log('changes:', changes);
console.log('referrals after:', referrals);
});