从[重复]中的现有数组创建一个新数组答案

【问题标题】：Create a new Array from Existing array in [duplicate]从[重复]中的现有数组创建一个新数组
【发布时间】：2018-12-19 03:25:04
【问题描述】：

我有一个像这样的现有数组

"activeSubject": [
        {
            "subject_id": "Class Teacher",
            "subject_name": "Class Teacher",
            "status": "2"
        },
        {
            "subject_id": "Academic Leader (Head)",
            "subject_name": "Academic Leader (Head)",
            "status": "2"
        },
        {
            "subject_id": "15",
            "subject_name": "Physics",
            "status": "2"
        }
    ]

然后我想创建一个看起来像这样的新数组

"new_subjects": [
        {
            "value": "Class Teacher",
        },
        {
            "value": "Academic Leader (Head)",
        },
        {
            "value": "Physics",
        }
    ]

我已经用map()方法试过了

var objA = this.state.activeSubject.map(o => ({
          [o]: { value: o.subject_name}
        }))

但它没有给出正确的数组，请帮我解决这个问题

【问题讨论】：

标签： javascript reactjs react-native

【解决方案1】：

你的map 语法很奇怪，我不知道你想做什么，但这应该足够了;)

this.state = {"activeSubject": [
    {
        "subject_id": "Class Teacher",
        "subject_name": "Class Teacher",
        "status": "2"
    },
    {
        "subject_id": "Academic Leader (Head)",
        "subject_name": "Academic Leader (Head)",
        "status": "2"
    },
    {
        "subject_id": "15",
        "subject_name": "Physics",
        "status": "2"
    }
]};

var objA = this.state.activeSubject.map(o => ({ value: o.subject_name}));
console.log(objA);

【讨论】：

并不奇怪，只是这里不正确。 foo = { [o]: v } 与 foo = {}; foo[o] = v 相同；它被称为“计算属性名称”。这是该语言的最新添加，非常受欢迎，但在这种情况下这样做是错误的。
是的，这确实让人感觉过于复杂。

【解决方案2】：

var activeSubject = [
    {
        "subject_id": "Class Teacher",
        "subject_name": "Class Teacher",
        "status": "2"
    },
    {
        "subject_id": "Academic Leader (Head)",
        "subject_name": "Academic Leader (Head)",
        "status": "2"
    },
    {
        "subject_id": "15",
        "subject_name": "Physics",
        "status": "2"
    }
];
let newSubject = [];
activeSubject.forEach((obj) => { newSubject.push({ 'value:' obj.subject_name}); });
console.log(newSubject);

【讨论】：

你为什么要在上面写forEach？ .map 为你做这件事，并为此而建
对不起...我不习惯使用 .map - 主要在不支持 .map 的旧 rhino 引擎上工作
我猜这是你可以做到的方式

【解决方案3】：

这样的事情会起作用

this.state = {"activeSubject": [
    {
        "subject_id": "Class Teacher",
        "subject_name": "Class Teacher",
        "status": "2"
    },
    {
        "subject_id": "Academic Leader (Head)",
        "subject_name": "Academic Leader (Head)",
        "status": "2"
    },
    {
        "subject_id": "15",
        "subject_name": "Physics",
        "status": "2"
    }
]};

let objA = this.state.activeSubject.map(({ subject_name: value}) => ({ value }));

console.log(objA)

【讨论】：

【解决方案4】：

您可以将destructuring assignment 与object property assignment pattern [YDKJS: ES6 & Beyond] 结合使用，并将value 与short hand property 结合使用。

var array = [{ subject_id: "Class Teacher", subject_name: "Class Teacher", status: "2" }, { subject_id: "Academic Leader (Head)", subject_name: "Academic Leader (Head)", status: "2" }, { subject_id: "15", subject_name: "Physics", status: "2" }],
    result = array.map(({ subject_name: value }) => ({ value }));

console.log(result);

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【讨论】：