tengo este código que da el error "Error: no capturado (en promesa): TypeError: this.weekMap.get no es una función". ¿Por qué weekMap no se reconoce como un objeto de mapa?

 let weekMap: Map<string, ExerciseDay>; let jsonWeekMap =require('./initialWeekMap.json'); weekMap=jsonWeekMap as Map<string, ExerciseDay>; console.log("week data got:"+weekMap.get("Monday"))

El archivo Json contiene:

 { "Monday":{ "englishDayName":"Monday", "dayNameTranslated":"Monday", "counter":0, "exerciseList":[] }, "Tuesday":{ "englishDayName":"Tuesday", "dayNameTranslated":"Tuesday", "counter":0, "exerciseList":[] }, "Wednesday":{ "englishDayName":"Wednesday", "dayNameTranslated":"Wednesday", "counter":0, "exerciseList":[] }, "Thursday":{ "englishDayName":"Thursday", "dayNameTranslated":"Thursday", "counter":0, "exerciseList":[] }, "Friday":{ "englishDayName":"Friday", "dayNameTranslated":"Friday", "counter":0, "exerciseList":[] }, "Saturday":{ "englishDayName":"Saturday", "dayNameTranslated":"Saturday", "counter":0, "exerciseList":[] }, "Sunday":{ "englishDayName":"Sunday", "dayNameTranslated":"Sunday", "counter":0, "exerciseList":[] }

}