推送到地图/承诺中的新数组 [英] Push to a new array inside a map/promise

问题描述

这是我当前设置的简化版本.

Here is a simplified version of my current setup.

运行此代码时，您会注意到修改 changes 数组也会操纵原始的 referrals 数组.这是因为我要在地图函数中 push 到 changes 数组吗?如何修改 changes 数组而不修改 referrals 数组?

When running this code you'll notice that modifying the changes array also manipulates the original referrals array. Is this because I'm pushing to the changes array inside a map function? How can I modify the changes array without modifying the referrals array?

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);
});

推荐答案

您只需要创建内部对象的深层副本，就可以使用lodash deepClone或split运算符来完成它.

You just need to create a deep copy of the inner objects, you can do it with lodash deepClone, or spread operator.

类似的东西:

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);
});

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