Question

我正在开发一个Ionic 3项目，其中响应http数据采用JSON数组格式（来自控制台）：Country Array（5）

0: {record_id: "1", local_TimeStamp: "16:00:00", country: "USA"}
1: {record_id: "2", local_TimeStamp: "17:00:00", country: "Japan"}
2: {record_id: "3", local_TimeStamp: "17:00:00", country: "Korea"}
3: {record_id: "4", local_TimeStamp: "15:00:00", country: "Thailand"}
4: {record_id: "5", local_TimeStamp: "16:00:00", country: "China"}

如何（1）删除上述项之一（2）附加到上述JSON数组的最后一个索引。注意：由于一些特殊的视图要求，步骤1和2需要分开。所以结果JSON数组看起来像这样：

0: {record_id: "1", local_TimeStamp: "16:00:00", country: "USA"}
1: {record_id: "2", local_TimeStamp: "17:00:00", country: "Japan"}
3: {record_id: "4", local_TimeStamp: "15:00:00", country: "Thailand"}
4: {record_id: "5", local_TimeStamp: "16:00:00", country: "China"}
2: {record_id: "3", local_TimeStamp: "17:00:00", country: "Korea"}  <- Moved

我试过这段代码：

country.splice(country.findIndex(e => e.country === 'Korea'),1);
country = [...country];
// From console it's OK. Record deleted.
// Next append the element back:
country.push({record_id: "3", local_TimeStamp: "17:00:00", country: "Korea"});
country = [...country];
// From console looks OK. Element appended to the last index of the Json array.

但如果我再次运行代码：

country.splice(country.findIndex(e => e.country === 'Korea'),1);

再也找不到韩国元素了。

Answer 1

看起来你正在使用扩展运算符进行一些不必要的解构。这是一个使用函数的简单示例：

示例

Answer 2

你可以这样做：

let country = [
    { record_id: "1", local_TimeStamp: "16:00:00", country: "USA" },
    { record_id: "2", local_TimeStamp: "17:00:00", country: "Japan" },
    { record_id: "3", local_TimeStamp: "17:00:00", country: "Korea" },
    { record_id: "4", local_TimeStamp: "15:00:00", country: "Thailand" },
    { record_id: "5", local_TimeStamp: "16:00:00", country: "China" }
];
const korea = country.splice(country.findIndex(e => e.country === 'Korea'), 1);
country = [...country, ...korea];

Answer 3

使用array.prototype.slice，array.prototype.find和spread：

＆＃13;

var arr = [
    {record_id: "1", local_TimeStamp: "16:00:00", country: "USA"},
    {record_id: "2", local_TimeStamp: "17:00:00", country: "Japan"},
    {record_id: "3", local_TimeStamp: "17:00:00", country: "Korea"},
    {record_id: "4", local_TimeStamp: "15:00:00", country: "Thailand"},
    {record_id: "5", local_TimeStamp: "16:00:00", country: "China"}
];

var index = arr.findIndex(e => e.country === "Korea");    
var a = arr.slice(0, index);
var b = arr.slice(index + 1);
var c = arr.find(e => e.country === "Korea");

var result = [...a, ...b, c];

console.log(result);

＆＃13;

Answer 4

Renato Gama的评论可能会为您解决问题。但是如果你需要单独执行这些步骤：

如何（1）删除上述项目之一

您可以使用Array.prototype.filter获取没有特定记录的数组，例如：myArray.filter(record => record.country !== "Korea")。但考虑到您想再次添加记录，可以使用Array.prototype.splice，如下所示：

var removed = myArray.splice(/* arguments */);

上面是第1步，第2步将再次推动它 - myArray.push(removed);

但如果我再次运行代码：

country.splice（country.findIndex（e =＆gt; e.country ==='Korea'），1）;

再也找不到韩国元素了。

您找不到该元素，因为您使用splice将其删除，并且未将已删除的元素保存到变量中。

Answer 5

这样的事情可能会这样做，虽然你在预期输出中提供的指数对我没有意义：

const originalCountries = [
  {record_id: "1", local_TimeStamp: "16:00:00", country: "USA"},
  {record_id: "2", local_TimeStamp: "17:00:00", country: "Japan"},
  {record_id: "3", local_TimeStamp: "17:00:00", country: "Korea"},
  {record_id: "4", local_TimeStamp: "15:00:00", country: "Thailand"},
  {record_id: "5", local_TimeStamp: "16:00:00", country: "China"}
];

const removeCountry = (name, countries) => {
  const idx = countries.findIndex(c => c.country === name);
  return idx > -1 
      ? {
           countries: countries.slice(0, idx).concat(countries.slice(idx + 1)), 
           country: countries[idx]
        }
      : {countries, country: null};
};

const addCountry = (country, countries) => countries.concat(country);

console.log('Step 1');
const {countries, country} = removeCountry('Korea', originalCountries);
console.log(countries);

console.log('Step 2');
const updatedCountries = addCountry(country, countries);
console.log(updatedCountries);

如何在JSON数组中删除和追加元素？

5 个答案: