How to return company name from service json ?

Question

cannot return company name from json 

i have company service as below :

getCompanyDetails(companyID) {
    return this.http.get(this.rootURL + companyID);
  }

This service above return following json :

{"CompanyID":0,"CompanyName":"ASE Industrial Holding Co., Ltd.","CountryName":"Taiwan","LogoSourceUrl":null,"MainWebSite":"http://www.aseglobal.com/","CompanyType":"Public","Taxonomy":"Test \u0026 Assembly","RevenueYear":"","TotalRevenue":"","YearToYearGrowth":"","NumberOfEmployees":"1017","Score":"","NumberMergerAndAcquisitions":"3"}

I need to return  value  ASE Industrial Holding Co., Ltd

to attribute  CompanyName

 

companyname: string;
this.companyService.getCompanyDetails(CompanyID)
this.companyname=???????????????

how to call service to return value of CompanyName based on CompanyId