JavaScript - get last day of month

In this article, we would like to show you how to get the last day of the month in JavaScript.

Quick solution:

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const date = new Date('2021-08');

const lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

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console.log(lastDay.toISOString());  // 2021-08-30T22:00:00.000Z

In this example, we use:

• date.getFullYear() - to get the year of the specified date,
• date.getMonth() - to get the month of the specified date +1 so we get the next month,
• 0 in the Date() constructor stands for the day of the month (the last day of the previous month in our case).

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const date = new Date('2021-08-30');

const lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

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console.log(lastDay.toISOString());  // 2021-08-30T22:00:00.000Z

Output:

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2021-08-30T22:00:00.000Z

• Date() constructor syntax - JavaScript