get week of year in javascript

To get the week of the year in JavaScript, we can use the Date() constructor and various methods provided by it. Here's an example snippet that can give us the week of the year:

index.tsx
const today = new Date();
const firstDayOfYear = new Date(today.getFullYear(), 0, 1);
const pastDaysOfYear = (today - firstDayOfYear) / 86400000; // 86400000 milliseconds = 1 day
const weekOfYear = Math.ceil((pastDaysOfYear + firstDayOfYear.getDay() + 1) / 7);

console.log(`Week of the year: ${weekOfYear}`);
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Here, we first create a Date object with the current date. Then, we create another Date object for the first day of the year by passing the year and January 1 as arguments. We then calculate how many days have passed since the first day of the year by subtracting the first day of the year from the current date and dividing by the number of milliseconds in a day.

Then, we add the day of the week of the first day of the year and 1 (since the first week of the year can start on any day), and divide by 7 to get the current week of the year. Finally, we round up to the nearest integer using Math.ceil().

This method should work for most cases, but there may be some variations in how different countries define their calendar weeks.