One more abstraction of the gradeschool.ts

grade-school.ts

class GradeSchool{
    private _studentRoster: Map<number,string[]> = new Map();

    public studentRoster(): Map<string,string[]> {
        const rosterMap: Map<string,string[]> = new Map();
        for(const key of this._studentRoster.keys()){
            rosterMap.set(key.toString(),this.studentsInGrade(key));
        }
        return rosterMap;
    }

    public addStudent(name: string, grade: number){
        let studArray: string[] = this.studentsInGrade(grade).concat(name);
        this._studentRoster.set(grade,studArray);
    }

    public studentsInGrade(grade: number): string[]{       
        return [...(this._studentRoster.get(grade)|| []).sort()];
    }

}


export default GradeSchool;