在循环

Question

我有这样的数据集：

[
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
]

现在为了逐个获取值，我创建了一个循环。在循环下我得到了价值。

Now if I want to add extra key value on that object then how it will be done.?

我试过数据[i] .extrakey =“value”; 的console.log（数据）; 但它不会设置。

非常感谢任何帮助

Answer 1

使用map

array = array.map( s => Object.assign( s, {extrakey : "value" } ) );

Answer 2

您可以在下面的示例中看到它。只是迭代数组并添加一个新键将改变数组中的对象，因为object是一个引用类型，你只是使用一个更改原始对象的引用。

const array = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        }
];

array.forEach(item => item.extraKey = 'value');

console.log(array);

此外，如果您想更改数组项，最好不要更改原始对象，而是创建副本并提供新数组。

const array = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        }
];

const newArray = array.map(item => Object.assign({}, item, { extraKey: 'value' }));

console.log(newArray);

Answer 3

您可以使用spread和array.prototype.map添加额外的密钥：

var arr = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
];

var result = arr.map(e => ({...e, extraKey: 'value'}));

console.log(result);

Answer 4

var array = [
    {
        "_id": "5aa7b6add9655d0bd4ce1f53",
        "user_name": "as",
        "createdate": "2018-03-13T11:31:57.133Z",
    },
    {
        "_id": "5aa7b6add9655d0bd4ce1f54",
        "user_name": "ds",
        "createdate": "2018-03-13T11:31:57.133Z",
    }
];
array = array.map( s => Object.assign( s, {extrakey : "value" } ) );