推送到map/promise中的新数组

Question

这是我当前设置的一个简化版本。

在运行这段代码时，您会注意到修改changes数组也会操作原始的referrals数组。这是因为我要在push函数中对changes数组执行push操作吗？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

你只需要创建一个内部对象的深层副本，你可以用lodash deepClone或spread操作符来做。

大概是这样的：

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);
});

Answer 2

感谢blex带我经历了这里发生的一切。本质上，当我将对象推入一个新数组时，我推送的是整个引用，而不仅仅是一个副本。使用Object.assign克隆对象解决了我的问题。

以下是整个编辑以供参考：

​

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) {
  new Promise(function(resolve, reject) {
    if (referral.change) {
      changes.push(Object.assign({}, 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);
});

​