如何在不影响原始数组的情况下删除值和键？

Question

当我运行下面的代码时，listData（原始数据源）也将受到影响。

如何改善代码，以便downloadData可以从listData复制数据并删除数组中的id，createBy，create_at，updatedBy和updated_at，但listData的数据将保留且未更改？

let downloadData = this.listData.filteredData;

let downloadDataNum = downloadData.length;

for( let i = 0; i < downloadDataNum; i++ ) {
  delete downloadData[i].id;
  delete downloadData[i].createdBy;
  delete downloadData[i].created_at;
  delete downloadData[i].updatedBy;
  delete downloadData[i].updated_at;
}

Answer 1

您可以尝试使用"..."深拷贝

let downloadData = [...this.listData.filteredData];

let downloadDataNum = downloadData.length;

for( let i = 0; i < downloadDataNum; i++ ) {
  delete downloadData[i].id;
  delete downloadData[i].createdBy;
  delete downloadData[i].created_at;
  delete downloadData[i].updatedBy;
  delete downloadData[i].updated_at;
}

让我知道它是否有效。

Answer 2

 let downloadData = [...this.listData.filteredData];

for( let i = 0; i < downloadData.length; i++ ) {
  delete downloadData[i].id;
  delete downloadData[i].createdBy;
  delete downloadData[i].created_at;
  delete downloadData[i].updatedBy;
  delete downloadData[i].updated_at;
}

您可以尝试...使用传播运算符，您可以将数据传播到downloadData变量，而无需更改listData

Answer 3

您应该使用JSON.stringify()和JSON.parse()

复制原始数据

let downloadData = JSON.parse(JSON.stringify(this.listData.filteredData));

您还可以使用forEach键数组来简化代码。

let keys = ['id','createdBy','created_at','updatedBy','updated_at'];
downloadDataNum.forEach(x => {
     keys.forEach(key => delete x[key]);
})

使用map()和reduce()

您可以在原始数组上使用map()并返回包含所需属性的新数组

let keys = ['id','createdBy','created_at','updatedBy','updated_at'];
let downloadData = this.listData.filteredData.map(x => {
     return keys.reduce((ac,a) => (ac[a] = x[a],ac),{})
});

Answer 4

在编辑数组之前先对其进行克隆，因为数组是通过引用复制的：

let downloadData = this.listData.filteredData;

// Clone the array
let cloneDownloadData = downloadData.slice(0);

let downloadDataNum = cloneDownloadData.length;

for( let i = 0; i < downloadDataNum; i++ ) {
  delete cloneDownloadData[i].id;
  delete cloneDownloadData[i].createdBy;
  delete cloneDownloadData[i].created_at;
  delete cloneDownloadData[i].updatedBy;
  delete dcloneDownloadData[i].updated_at;
}

Answer 5

您必须复制原始数据。

您可以通过以下几种方法执行此操作：

// Way 1
let downloadData = Array.from(this.listData.filteredData);

// Way 2
let downloadData = JSON.parse(JSON.stringify(this.listData.filteredData));

// Way 3 (using spread operator)
let downloadData = [...this.listData.filteredData];

// Way 4
let downloadData = this.listData.filteredData.slice(0);

那么您添加到downloadData的任何修改都不会影响原始数据。