![]() You can also use the Date.parse() method to return the number of milliseconds since the epoch (January 1st, 1970): Date.parse('') // 86400000ĭate.parse('') // 1560610800000 Setting a time zone All of the examples below return valid Date objects: new Date('2019-06') // June 1st, 2019 00:00:00 Getting the date this way is very flexible. ![]() Get a date and time from a string const stringDate = new Date('15:00:00') Will return Friday, January 2nd, 1970 (UTC). In a day there's 86,400,000 milliseconds so: const dayAfterEpoch = new Date(86400000) New Date(ms) returns the date of the epoch plus the number of milliseconds you pass in. The Unix Epoch is important because it's what JavaScript, Python, PHP, and other languages and systems use internally to calculate the current time. This represents the time at Thursday, January 1st, 1970 (UTC), or the Unix Epoch time. Get a date and time from a timestamp const uni圎poch = new Date(0) Note that the months are zero-indexed, beginning with January at 0 and ending with December at 11. The syntax is Date(year, month, day, hour, minute, second, millisecond). Mon 12:58:21 GMT-0400 (Eastern Daylight Time) Get a date and time with individual values const specifiedDate = new Date(2019, 4, 29, 15, 0, 0, 0) How to Create a Date Object Get the current date and time const now = new Date() This tutorial will teach you everything you need to know about working with dates and times in your projects. For validating that the requestBody has a property of the DateTime string format, this is a simple way of how we can create a function to check it.Welcome to our ultimate guide on the JavaScript Date object and Moment.js. That way, we will get 3 unique moment objects and their respective datetime values.įor backend applications, it is pretty common to validate that the properties found in the request body are the specified type that we expect them to be. const today = moment()Ĭonst oneWeekLater = today.clone().add( 1, "week")Ĭonst twoWeeksLater = today.clone().add( 2, "week") Hence, the solution to this problem is rather straight forward - we simply have to clone the moment object before performing arithmetic operations. add, moment mutates the original object rather than mutating a copy of that object. This is because it turns out that all 3 constants refer to the same moment object, with the same datetime value. However, when we log the 3 values, it turns out that they all have the same date. const today = moment()Ĭonst oneWeekLater = today.add( 1, "week")Ĭonst twoWeeksLater = today.add( 2, "week") Instead of constantly writing hard coded values like “”, “”, I could create relative moment objects for testing. In many DateTime manipulation test cases, we would want to create DateTime objects in a chronological order. Otherwise you can refer to the source code found here at this GitHub repository on how Jest can be setup for a simple Node.js project. If you are not familiar with Jest or find it a bother to set it up, you can also simply console.log the relevant variables to check the values manually. There will also be Jest tests in the article to illustrate that the functionalities work as intended. Some examples given here are inspired based on what I have done at work. And for those who don’t have to, this article also serves as an interesting read for those who are curious about problems that can come from Moment.js & working with DateTime. Hence, this article is meant to highlight some strange gotchas for anyone who still has to deal with Moment.js. Nonetheless, there are many developers who still have to work with this library because many existing production projects use it heavily, and it take significant effort to do a code revamp to migrate to use another immutable datetime library. Even the library maintainers themselves discourage you to use Moment.js in new projects going forward. Moment.js is the most commonly used JavaScript library to deal with datetimes, however for many use cases today, it may not be the best library to use given the issues of mutability, file size bundles and that it was designed for the previous era of the JavaScript ecosystem. ![]()
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