singletone.js

const getAppEnv = (function(){

  class AppEnv{
    
    constructor(platform, buildVersion){
      this.platform = platform;
      this.buildVersion = buildVersion;
      this.cacheEnabled = false;
    }
    enableCache(){
      this.cacheEnabled = true;
    }
  }
  
  let appEnv = null;

  
  return function(){
      if(appEnv == null){
          console.log("Fetching for the first Time");
          appEnv = new AppEnv("unix","10.1.1");
          
      }else{
          console.log("Fetching second Time");
      }
    return appEnv;
    }
  
  
}());


p = getAppEnv();
console.log(p.cacheEnabled);
c = getAppEnv();
console.log(c.cacheEnabled);
p.enableCache()
console.log(p.cacheEnabled);
console.log(c.cacheEnabled);