I need to fill missing business days (i.e. any days except saturday and sunday) in a series. So let's say I have this array:

const arr =  [
    "Date,Value",
    "2020-12-31,1",
    "2021-01-01,-3",
    "2021-01-04,-38",
    "2021-01-05,-14",
    "2021-01-07,27",
    "2021-01-08,55",
]

"2021-01-06" is a wednesday, but is missing in the array. What I need to do then is to take the value from the day before (-14) and use it for "2021-01-06". At the end it would look like this:

[
    "Date,Value",
    "2020-12-31,1",
    "2021-01-01,-3",
    "2021-01-04,-38",
    "2021-01-05,-14",
    "2021-01-06,-14",
    "2021-01-07,27",
    "2021-01-08,55",
]

Currently Im using this algorithm (which seems to work), but I wonder if it can be done more efficiently:

const fixEmptyBusinessDays = (arr) => {
    const newArr = [];
    if(arr.length){
        newArr.push(arr[0]);
        arr.shift();
        let latestValue = 0;
        for(let i = 0;i<arr.length;i++){
            const el = arr[i];
            if(el && el.length){
                newArr.push(el);
                if(el.length > 1){
                    const val = el[1];
                    latestValue = val;
                }
                const currDate = el[0];
                const currDateAsDateObject = new Date(currDate);
                if(currDate && currDateAsDateObject){
                    const day = currDateAsDateObject.getDay();
                    if((i+1)<arr.length && arr[i+1] && arr[i+1].length){
                        const next = arr[i+1];
                        const nextDayInFile = next[0];
                        const nextWeekDayUnformatted = get_next_weekday(new Date(currDate));
                        const nextMonth = (nextWeekDayUnformatted.getMonth()+1) < 10 ? `0${(nextWeekDayUnformatted.getMonth()+1)}` : (nextWeekDayUnformatted.getMonth()+1);
                        const nextDay = nextWeekDayUnformatted.getDate() < 10 ? `0${nextWeekDayUnformatted.getDate()}` : nextWeekDayUnformatted.getDate();
                        const nextWeekDay = `${nextWeekDayUnformatted.getFullYear()}-${nextMonth}-${nextDay}`
                        if(nextDayInFile !== nextWeekDay){
                            newArr.push([nextWeekDay, latestValue]);
                        }
                    }
                }
            }
        }
    }
    return newArr;
}
const arr =  [
    "Date,Value",
    "2020-12-31,1",
    "2021-01-01,-3",
    "2021-01-04,-38",
    "2021-01-05,-14",
    "2021-01-07,27",
    "2021-01-08,55",
]
const result = fixEmptyBusinessDays(arr);