typescript - use map

• Commit 

https://github.com/shooeugenesea/study-js/commit/2d22117a7b36ea1225b960892995e409bbc5e64f

https://github.com/shooeugenesea/study-js/commit/30cb24cd3a5dc57dde750fa6e90a04b88dba8084

• Declare class with map
export class TestMap {

    private map: Map<string, string> = new Map();


    put(key:string, val:string): void {
        if (key) {
            this.map.set(key, val);
        }
    }


    get(key:string): string | undefined {
        if (key) {
            return this.map.get(key)
        }
    }


    count(): number {
        return this.map.size;
    }


    clearByKeyPrefix(prefix: string) {
        this.map.forEach((v: string, k:string, m:Map<string,string>) => {
            if (k.startsWith(prefix)) {
                m.delete(k);
            }
        })
    }
}
• Put and get then print
const testMap = new TestMap();
testMap.put("ka", "vka");
testMap.put("kb", "vka");
testMap.put("kc", "vka");
testMap.put("kd", "vka");
testMap.put("ke", "vka");
testMap.put("aa", "vaa");
console.log(testMap);
console.log(testMap.count()); // 6
testMap.clearByKeyPrefix("k"); // print 6 entries
console.log(testMap.get("aa")); // print vaa