如何根据 Map<K,V> key 和 value 类型做逻辑？

Question

出于序列化的目的，必须根据键和值类型分离不同的 Map 类型和驱动逻辑。如何在 Typescript 中完成？

例如

const stringAndNumberPairs: Map<string, number> = new Map<string, number>([['text', 1]]);
const stringAndStringPairs: Map<string, string> = new Map<string, string>([['text', 'more text']]);

功能类似于

function serialize(input: any): string {
  let output: string = "";
  if (type of K is number) {
    output += "Key is number"; 
  }

  if (type of V is string) {
    output += "Value is string";
  }
  else if (type of V is number) {
    output += "Value is number";
  }

  return output;
}

Answer 1

typeof（对于基本类型）或 instanceof（对于 class 实例）是您要查找的关键字。

class Foo { }


function serialize<K, V extends any>(map: Map<K, V>): string {
    let output: string = "";

    Array.from(map.entries()).forEach(([k, v]) => {
        if (typeof k === 'number') {
            output += "Key is number";
        }

        if (typeof v === 'string') {
            output += "value if string"
        }

        if (v instanceof Foo) {
            output += "value if string"
        }
    });
    return output;
}

或者更简洁的方式：

function serialize<K, V extends any>(map: Map<K, V>): string[][] {

  const output = Array.from(map.entries()).map(([k, v]) => {
    return [
      { condition: typeof k === 'number', label: 'Key is number' },
      { condition: typeof v === 'string', label: "value is string" },
      { condition: v instanceof Foo, label: 'value is class Foo' }

    ].filter((c) => c.condition).map((c) => c.label)  // you could join() here

  });
  return output  // also join() here
}

https://www.typescriptlang.org/play?ssl=16&ssc=2&pln=1&pc=1#code/MYGwhgzhAEBiD29oG9oF8CwAob2BmArgHbAAuAlvEdBAKYBO5YI5AXrQDwDSANNAGrRaAD1K0iAExhgiATwB8ACgC2YAA4AuaAFl13Pv3kBKLRFKMiAcwDaAXTspcWaNGBUz0eAVJrv0ALzQAIL09GCyAHR49PDKKuoR4ubktBCKRkYRqmqKitYA1nwAbrZGAfKOzi7Q9LSkBPTU1tjV1ahukuQUVFqksmq08HjQ+QH+gQDkRATKAEYME3zg8yBaE1y0stDkMNNzC+g8La0orlQSXZREvf2Dw0Vjk2YWlovQy7Sr0ABERcwEtG2MGe5Cs30Ox1a7XOlx60AeoLMMmAdzgiCWYBWaz+IABQNc4CgaPgE3QTlatii5BAYnouWAZX8FWAEQ6F26REy2XpjOZEQ+IDK0AA9MLoLIvK4ZNAAFbwUHpaAACwYtHJ6CMAG5jrV6o1PN5fKQXKLoMwIEg5Qqyiratg0EA

如何根据 Map<K,V> key 和 value 类型做逻辑？

How to do logic based on Map<K,V> key and value types?

generics

typescript