How to loop through object of strings with dates in typescript?

I have object, keys are dates, before dot are months, after are years:

const dataObj = {
  '01.2015': 0.01,
  '02.2015': 0.10,
  '03.2015': 0.05,
  '04.2015': 0.25,
  // ...
}

the function takes two dates and return an array with objects containing values from the dataObj

interface Point {
  date: string;
  value: number;
}

type Digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9';
type Day = `${Digit}${Digit}`;
type Month =
  | '01'
  | '02'
  // ...
  | '11'
  | '12';

type Year = '2015' | '2016' | '2017';
type DateString = `${Day}.${Month}.${Year}`;

type MonthDateString = `${Month}.${Year}`;

function count(firstDate: DateString, secondDate: DateString): Point[] {
 const result: Point[] = [];
 let currentDate = firstDate.slice(3) as MonthDateString;
 // loop through dataObj and push in result
 return result // [{date: '01.2015', value: 0.01}, {...}, ...]
}

How to loop through dataObj? I tried for loop

for(let i = currentDate; i !== secondDate.slice(3);  )

but have no idea what to do with final-expression, how to update counter variable, pass next key(string with date) from dataObj.