Populating an array of object with 0 if object does not exist

I am building a chart for monthly data which would have the x axis as wk1 – wk4 and y axis being the amount of goods etc. I was able to build out a solution but the problem lies when there is no data for a particular week. This is my code below.

    const byAmount = obj => {
    const res = [];
    const keys = Object.keys(obj);
    keys.forEach(key => {
        res.push({
            week: `wk${key}`,
            amount: obj[key]
        });
    });
    return res.sort((a, b) => a.amount - b.amount).slice(0, 5);;
};

const getWeeklyFromMonth = (arr, month) => {
    const week = arr.map(a => ({ ...a, week: Math.floor((moment(a.dateScanned.$date).date() - 1) / 7) + 1 }));
    let dataForMonth = [];
    let total;
    week.map(data => {
        if (moment(data.dateScanned.$date).format("MMM") === month) {
            dataForMonth.push(data);
            const totalPerWeek = dataForMonth.reduce((acc, cur) => {
                acc[cur.week] = acc[cur.week] + cur.amount || cur.amount;
                return acc;
            }, {});
            total = totalPerWeek;
        }
    });


    return byAmount(total);


}

When I run this I get the below:

[
  { week: 'wk1', amount: 14 },
  { week: 'wk2', amount: 27 },
  { week: 'wk4', amount: 43 }
]

This is fine but I want to populate the array with 0 if there is no data say for week 3. I would want it to be this

[
  { week: 'wk1', amount: 14 },
  { week: 'wk2', amount: 27 },
  { week: 'wk3', amount: 0  },
  { week: 'wk4', amount: 43 }
]

I was thinking of having an array of like [1, 2, 3, 4] and if the array includes the week number, pop it out of the array and then the remaining item should be used to populate it but I find myself scratching my head. Does anyone know a decent way to do this?

Thank you in advance.

>Solution :

You can try this:

const byAmount = obj => {
    const res = [];
    const keys = Object.keys(obj);
    const [min, max] = [Math.min(...keys), Math.max(...keys)];
    for(let key = min; key <= max; key++) {
        res.push({
            week: `wk${key}`,
            amount: obj[key] || 0
        });
    }
    return res.sort((a, b) => a.amount - b.amount).slice(0, 5);;
};