how to use the differenceinhours function from date-fns in javascript

To use the differenceInHours function from the date-fns library in JavaScript, first, you need to install it using npm:

index.tsx
npm install date-fns
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Then, you can import the function in your JavaScript code as follows:

index.tsx
const { differenceInHours } = require('date-fns');
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The differenceInHours function takes two arguments, both of which should be valid Date objects or parsable date-time strings:

index.tsx
const date1 = new Date('2021-07-01T10:30:00Z'); // July 1, 2021 at 10:30:00 AM UTC
const date2 = '2021-06-01T10:30:00-05:00'; // June 1, 2021 at 10:30:00 AM in UTC-05:00 timezone

const hoursDiff = differenceInHours(date1, date2); // returns 1032 (total hours between two dates)
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In the example above, we are calculating the difference in hours between two dates, one specified using a Date object and the other using a date-time string in a specific timezone. The function returns the total hours between the two dates, taking into account any daylight saving time changes between them.

Note that you can also pass an optional third argument to ignore any fractional hours in the result:

index.tsx
const hoursDiff = differenceInHours(date1, date2, {roundingMethod: 'ceil'}); // returns 1033 (rounded up to highest hour difference)
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You can find more information about this function and other date-fns functions in the official documentation.