如何以编程方式枚举枚举类型？ [英] How to programmatically enumerate an enum type?

问题描述

假设我有一个TypeScript 枚举， MyEnum ，如下所示：

Say I have a TypeScript enum, MyEnum, as follows:

enum MyEnum {
    First,
    Second,
    Third
}

在TypeScript 0.9.5中生成 enum 数组的最佳方法是什么？价值观？示例：

What would be the best way in TypeScript 0.9.5 to produce an array of the enum values? Example:

var choices: MyEnum[]; // or Array<MyEnum>
choices = MyEnum.GetValues(); // plans for this?
choices = EnumEx.GetValues(MyEnum); // or, how to roll my own?

推荐答案

这是该枚举的JavaScript输出：

This is the JavaScript output of that enum:

var MyEnum;
(function (MyEnum) {
    MyEnum[MyEnum["First"] = 0] = "First";
    MyEnum[MyEnum["Second"] = 1] = "Second";
    MyEnum[MyEnum["Third"] = 2] = "Third";
})(MyEnum || (MyEnum = {}));

哪个对象是这样的：

{
    "0": "First",
    "1": "Second",
    "2": "Third",
    "First": 0,
    "Second": 1,
    "Third": 2
}

具有字符串值的枚举成员

TypeScript 2.4添加了枚举可能具有字符串枚举成员值的功能。因此，可能最终得到如下所示的枚举：

TypeScript 2.4 added the ability for enums to possibly have string enum member values. So it's possible to end up with an enum that look like the following:

enum MyEnum {
    First = "First",
    Second = 2,
    Other = "Second"
}

// compiles to
var MyEnum;
(function (MyEnum) {
    MyEnum["First"] = "First";
    MyEnum[MyEnum["Second"] = 2] = "Second";
    MyEnum["Other"] = "Second";
})(MyEnum || (MyEnum = {}));

获取会员名

我们可以看看上面的示例试图弄清楚如何获得枚举成员：

We can look at the example immediately above to try to figure out how to get the enum members:

{
    "2": "Second",
    "First": "First",
    "Second": 2,
    "Other": "Second"
}

这是我想出的内容：

const e = MyEnum as any;
const names = Object.keys(e).filter(k => 
    typeof e[k] === "number"
    || e[k] === k
    || e[e[k]]?.toString() !== k
);

成员值

一旦名称，我们可以通过以下操作遍历它们以获得相应的值：

Once, we have the names, we can loop over them to get the corresponding value by doing:

const values = names.map(k => MyEnum[k]);

扩展类

我认为最好的方法为此，是创建自己的函数（例如 EnumEx.getNames（MyEnum））。您不能向枚举添加函数。

I think the best way to do this is to create your own functions (ex. EnumEx.getNames(MyEnum)). You can't add a function to an enum.

class EnumEx {
    private constructor() {
    }

    static getNamesAndValues(e: any) {
        return EnumEx.getNames(e).map(n => ({ name: n, value: e[n] as string | number }));
    }

    static getNames(e: any) {
        return Object.keys(e).filter(k => 
            typeof e[k] === "number"
            || e[k] === k
            || e[e[k]]?.toString() !== k
        );
    }

    static getValues(e: any) {
        return EnumEx.getNames(e).map(n => e[n] as string | number);
    }
}

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