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.

Answer

There is some confusion in regards to the expected output. The function count needs to return a Point array which is an object array where each object has two props namely date (a string) and value (number, floating-point per inline-comments in the code).

It is assumed that the OP requires to find key-value pairs in dataObj such that the key (ie, month-year) is between firstDate and secondDate (which are parameters to count function).

Based on this assumption, the below code may achieve the desired objective (to generate an array of Point elements).

const isGreaterOrEqual = (dtOne: MonthDateString, dtTwo: MonthDateString) : Boolean => {
    const getYear = (dt: MonthDateString) : string => dt.slice(3);
    const getMonth = (dt: MonthDateString) : string => dt.substring(0, 2);
    return ((getYear(dtOne) > getYear(dtTwo)) ||
        (getYear(dtOne) === getYear(dtTwo) &&
            getMonth(dtOne) >= getMonth(dtTwo)
        )
    );
};

function count(firstDate: DateString, secondDate: DateString): Point[] {
 let beginDate = firstDate.slice(3) as MonthDateString;
 let endDate = secondDate.slice(3) as MonthDateString;
 return (
     Object.entries(dataObj)
     .filter(([k, v]) => isGreaterOrEqual(k as MonthDateString, beginDate) && isGreaterOrEqual(endDate, k as MonthDateString))
     .map(([k, v]) => ({ date: k, value: v} as Point))
    );
};

console.log(count( "01.01.2015" as DateString, "01.02.2015" as DateString));

TS Playground: Link here