I have a JS constructor function written in Typescript and i access this constructor function from other code like this

const ls = new LocalStorage<ICountryHolidayData>()
let strdVal = ls.getItem(constants.localStorageKey).storedValue

Though the code works fine but i do not get any intellisense..neither for ls.getItem nor for the storedValue property.

I think its because constructor functions can't inherit interface like classes do in typescript? Otherwise can some help me understand how to do this, so that i can get intellisense for both values. PS: i know the easier way is to use classes but i am curious on how to do it via constructor functions

export interface ILocalStorgaeReturnValue<Type>{
  storedValue: Type,
  date: Date
}

export interface ILocalStorage<Type extends {}>{

setItem(key:string,value:Type):void;
getItem(key:string):ILocalStorgaeReturnValue<Type>;
removeItem(key:string ):void;
//clear();
}



export function  LocalStorage<Type>(){  
  
  if( !window.localStorage)
      throw new Error(`Browser does not support local storage`)
 
 this.setItem = (key:string, val:Type ) =>{
   
  if(!key || !val )
    throw new Error(`key or value can not be null `)

    const completeObj = {
      storedValue: {
      ...val
      },
      date:new Date()
    }
    window.localStorage.setItem(key ,JSON.stringify(completeObj))
 },
 
 this.getItem = (key:string):ILocalStorgaeReturnValue<Type> =>{
   
 
  if(!key  )
    throw new Error(`[key can not be null `)

    
  const val= JSON.parse(window.localStorage.getItem(key))

  if(!val || Object.keys(val).length<2)
    return null 
  else 
    return <ILocalStorgaeReturnValue<Type>> {
      ...val
    }     
    
 },

 this.removeItem = (key:string) =>{
   
  if(!key  )
    throw new Error(`Key is empty`)

   window.localStorage.removeItem(key)
 }

}