将 Typescript Map<string, string> 转换为 json 字符串表示
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convert Typescript Map<string, string> to json string representation
提问by breezymri
I've got a Map<string, string>variable in typescript:
我Map<string, string>在打字稿中有一个变量：
let m = Map<string, string>().set('tag', 'v1');
I want to convert to json string representation:
我想转换为 json 字符串表示：
'{"tag": "v1"}'
I've tried 3 different ways. First is to use m.toString(). Second is using JSON.stringify(m). Both returned {}. I've even tried to convert the Mapto a javascript objectfirst and then convert to string:
我尝试了 3 种不同的方法。首先是使用m.toString(). 其次是使用JSON.stringify(m). 两人都回来了{}。我什至尝试先将 转换为Mapjavascript object，然后再转换为字符串：
function MapToString(map): string {
let ro = {};
Object.keys(map).forEach( key => {
ro[key] = map[key];
});
return JSON.stringify(ro);
}
s = MapToString(m);
This returned {}as well when I tried to print it in the console.
{}当我尝试在控制台中打印它时，这也返回了。
采纳答案by breezymri
回答by Lostfields
Readable? No, but it works
可读？不，但它有效
JSON.stringify(
Array.from(
new Map().set('tag', 'v1').set('foo', 'bar').entries()
)
.reduce((o, [key, value]) => {
o[key] = value;
return o;
}, {})
)
Like @james-hay pointed out, you have a typo that probably makes the object empty
就像@james-hay 指出的那样，你有一个可能使对象为空的错字
回答by Robert Hyman Will
Although it does not directly answer your question: when I had the same problem, I reconsidered my use of Map and went for plain JavaScript objects. Since JSON always needs strings as keys, one of Map's main advantages (keys of any type) are lost anyway.
虽然它没有直接回答你的问题：当我遇到同样的问题时，我重新考虑了我对 Map 的使用，并选择了纯 JavaScript 对象。由于 JSON 总是需要字符串作为键，因此 Map 的主要优势之一（任何类型的键）无论如何都会丢失。
Another advantage of Map is that they allow a nice type signature, like Map<String, Array<String>>. But here TypeScript's "index signatures" provide exactly this for plain JavaScript objects and even allow a name for keys:
Map 的另一个优点是它们允许很好的类型签名，例如Map<String, Array<String>>. 但是这里 TypeScript 的“索引签名”为纯 JavaScript 对象提供了这一点，甚至允许为键命名：
interface CityLists {
[postcode: string]: Array<string>
};
This can be used almost like a Map (with different syntax, of course) and it directly converts to JSON even when nested. I think the latter is quite important when you convert an object tree to JSON where maps can be nested somewhere deep down in other arbitrary objects and arrays.
这几乎可以像 Map 一样使用（当然，使用不同的语法），即使嵌套. 我认为当您将对象树转换为 JSON 时，后者非常重要，其中映射可以嵌套在其他任意对象和数组的深处。
Alternatively, TypeScript also has the type Record<K, T>for this use-case: a plain object used as a typed map. In the above example, I could write:
或者，TypeScript 也具有Record<K, T>此用例的类型：用作类型映射的普通对象。在上面的例子中，我可以写：
let cityLists: Record<string, Array<string>>;
cityLists["capitals"] = ["Rome", "Paris", "Berlin"];
