Time is but an Illusion.. in JavaScript! (JSConf JP)

With so much to worry about timing wise: formatting, time zones, internationalization, recurrence rules, leap years, daylight savings time, and more, everyone needs HELP!

Let’s turn time into money by taking a look at the most popular time libraries and how we use them to solve JavaScript’s time problems. We’ll look at how JavaScript’s Date object started and what its prototype allows. We’ll wind our way through dates, times, and standards to find solutions to the weirdness.

Let’s kill time together talking about JavaScript time! Because we know, time heals all.

Transcript

1. @mybluewristband TIME.. IS BUT AN ILLUSION IN JAVASCRIPT! @mybluewristband
2. @mybluewristband ୭Ͱ͔͢? Who am i? @mybluewristband
3. @mybluewristband Jennifer Wong Mode analytics Mozilla tech speaker whovian
4. @mybluewristband DOCTOR WHO Time Lord Sonic Screwdriver T.A.R.D.I.S Daleks @mybluewristband
5. @mybluewristband @mybluewristband
6. @mybluewristband Ͳ͏ͯ͠? What happened?
7. @mybluewristband RECURRING INVITES A past project @mybluewristband
8. @mybluewristband RECURRING INVITES Generate an recurrence rule (rrule) on the frontend (???) in iCal format All existing rrule libraries were 1.5+ years out of date But now there is an updated one: https://github.com/jakubroztocil/rrule So I wrote my own rrule library… Ensure timezone attached to rrule Timezone of office location, not employee Employees are based all over the world May create invites for people in other offices
9. @mybluewristband @mybluewristband
10. @mybluewristband @mybluewristband
11. @mybluewristband FREQ=WEEKLY; BYDAY=FR; UNTIL=20190629T120000Z;
12. @mybluewristband RECURRING INVITES - A PROBLEM We were in PST or GMT-7/GMT-8 (daylight savings) All tests would pass locally At 4pm/5pm PST/PDT, all frontend CI tests would fail for a few hours
13. @mybluewristband RECURRING INVITES - A PROBLEM Some tests written with assuming a specific time zone (PST/PDT) But the CI server was in a different timezone Tests didn’t expect that times minutes or hours apart might be in different days
14. @mybluewristband RECURRING INVITES - A SOLUTION KINDA Local testing vs CI testing issues Resolution: set a particular time/time zone in a test But this only reliably tests that specific time/time zone Also, undo any time mocking or the next test(s) will use the same time/time zone (and probably fail)
15. “ @mybluewristband Don't write your own recurrence rule library. Doubly so for JavaScript. Jennifer Wong
16. “ @mybluewristband Check the timezone of your CI server. Doubly so if it's running JavaScript tests. Jennifer Wong
17. @mybluewristband ࣌ؒͷෆࢥٞ͞ Time is weird. @mybluewristband
18. @mybluewristband @mybluewristband
19. @mybluewristband ࣌ؒ Tale as old as time @mybluewristband
20. @mybluewristband HISTORY OF TIME https://en.wikipedia.org/wiki/Time Artifacts from Paleolithic era suggest the moon was used to reckon time Lunar calendars Earliest lunar calendar was discovered in 8000 BC. Years of either 12 or 13 lunar months (354 or 384 days) Egyptians created first time measurement devices T-square Sundial Water clock
21. @mybluewristband TYPES OF TIME ZONES OR STANDARDS Greenwich Mean Time (GMT) Created in 1847 at the Royal Observatory in Greenwich Universal Coordinated Time (UTC) International Meridian Conference (of 26 nations) $ Colombia was there! & The United States was there! Unix Time Number of seconds that have passed since the Unix Epoch 00:00:00 UTC Thursday, 1 January 1970 International Standards Organization (ISO)
22. @mybluewristband G M T !!! @mybluewristband
23. @mybluewristband JAVASCRIPT DATE OBJECT It's old
24. @mybluewristband @mybluewristband
25. @mybluewristband ECMA-262 JavaScript! Version 1 - 1997 Only six new Date object methods have been added since then Date.prototype.toDateString() Date.prototype.toISOString() Date.prototype.toJSON() Date.prototype.toLocaleDateString() Date.prototype.toLocaleTimeString() Date.prototype.toTimeString()
26. @mybluewristband WHY THE 0 INDEX JavaScript’s Date object has a zero indexed month java.util.Date had 0-indexed month java.time package was released in 2014 with a 1-indexed month Moment.js uses a zero indexed month
27. @mybluewristband https://stackoverflow.com/questions/2552483/why-does-the-month-argument-range-from-0-to-11-in- javascripts-date-constructor/41992352#41992352
28. @mybluewristband https://stackoverflow.com/questions/2552483/why-does-the-month-argument-range-from-0-to-11-in- javascripts-date-constructor/41992352#41992352
29. “ @mybluewristband Because Java. Brendan Eich (creator of JavaScript)
30. @mybluewristband @mybluewristband
31. @mybluewristband TYPE COERCION One can coerce a date to a number of milliseconds from the Unix Epoch simply by using: +new Date() @mybluewristband
32. @mybluewristband JAVASCRIPT VERSUS MOMENT.JS FIGHT! @mybluewristband
33. @mybluewristband GETTERS Go get 'em
34. // Date Object Date.prototype.constructor Date.prototype.getDate() Date.prototype.getDay() Date.prototype.getFullYear() Date.prototype.getHours() Date.prototype.getMilliseconds() Date.prototype.getMinutes() Date.prototype.getMonth() Date.prototype.getSeconds() Date.prototype.getTime() Date.prototype.getTimezoneOffset() // Moment.js moment() moment().date() moment().day() moment().year() moment().hour() moment().millesecond() moment().minute() moment().month() moment().second() moment().get() moment().zone() // deprecated @mybluewristband
35. // Date Object Date.prototype.getUTCDate() Date.prototype.getUTCDay() Date.prototype.getUTCFullYear() Date.prototype.getUTCHours() Date.prototype.getUTCMilliseconds() Date.prototype.getUTCMinutes() Date.prototype.getUTCMonth() Date.prototype.getUTCSeconds() // Moment.js moment().utc().date() moment().utc().day() moment().utc().year() moment().utc().hour() moment().utc().milleseconds() moment().utc().minutes() moment().utc().month() moment().utc().seconds() @mybluewristband
36. @mybluewristband SETTERS Get, set, match (?) @mybluewristband
37. // Date Object Date.prototype.setDate() Date.prototype.setFullYear() Date.prototype.setHours() Date.prototype.setMilliseconds() Date.prototype.setMinutes() Date.prototype.setMonth() Date.prototype.setSeconds() Date.prototype.setTime() Date.prototype.setYear() // deprecated // Moment.js moment().date() moment().year() moment().hour() moment().millesecond() moment().minute() moment().month() moment().second() moment().set() moment().year() @mybluewristband
38. // Date Object Date.prototype.setUTCDate() Date.prototype.setUTCFullYear() Date.prototype.setUTCHours() Date.prototype.setUTCMilliseconds() Date.prototype.setUTCMinutes() Date.prototype.setUTCMonth() Date.prototype.setUTCSeconds() // Moment.js moment().utc().date() moment().utc().year() moment().utc().hour() moment().utc().milleseconds() moment().utc().minutes() moment().utc().month() moment().utc().seconds() @mybluewristband
39. @mybluewristband OTHER METHODS I've got gadgets and gizmos a-plenty @mybluewristband
40. @mybluewristband
41. // Date Object Date.prototype.toDateString() Date.prototype.toISOString() Date.prototype.toJSON() Date.prototype.valueOf() // Returns milliseconds since // the Unix epoch which is // 1 January 1970 00:00:00 UTC // Moment.js moment().format('ddd MMM DD YYYY’) moment().utc().format('YYYY-MM-DDTHH:mm:ss.SSS') + 'Z' moment().utc().format('YYYY-MM-DDTHH:mm:ss.SSS') + 'Z' parseInt( moment().format('x'), 10 ) // Returns the string version of milliseconds since // Unix epoch then parses into an integer @mybluewristband
42. // Date Object Date.prototype.toString() // e.g. Thu Oct 10 2019 22:46:02 // GMT-0700 (Pacific Daylight Time) Date.prototype.toTimeString() // e.g. 22:46:02 GMT-0700 // (Pacific Daylight Time) Date.prototype.toUTCString() // e.g. Fri, 11 Oct 2019 // 05:46:02 GMT // Moment.js moment().toDate().toString() // Translate into a Date object // then run .toString() on it moment().toDate().toTimeString() // Translate into a Date object // then run .toString() on it moment().utc().format( 'ddd, DD MMM YYYY HH:mm:ss' ) + ' GMT' @mybluewristband
43. @mybluewristband LOCALE STRINGS Whoa @mybluewristband
44. @mybluewristband LOCALE STRINGS Super cool! // Date Object Date.prototype.toLocaleDateString() Date.prototype.toLocaleString() Date.prototype.toLocaleTimeString() // Moment.js moment().format('L') moment().format('L, LTS') moment().format(‘LTS') moment().locale()
45. var event = new Date(Date.UTC(2012, 11, 20, 3, 0, 0)); var options = { weekday: ‘long', year: ‘numeric', month: ‘long', day: ‘numeric’ }; console.log(event.toLocaleDateString('de-DE', options)); // expected output: Donnerstag, 20. Dezember 2012 console.log(event.toLocaleDateString('ar-EG', options)); // expected output: ٢٠١٢ ،ﺮﺒﻤﺴﯾد ٢٠ ،ﺲﯿﻤﺨﻟا console.log(event.toLocaleDateString('ko-KR', options)); // expected output: 2012֙ 12ਘ 20ੌ ݾਃੌ @mybluewristband
46. @mybluewristband
49. @mybluewristband
50. @mybluewristband DEPRECATED Returned a two digit OR four digit year People didn’t think we’d live beyond the Mayan calendar https://developer.mozilla.org/en-US/ docs/Web/JavaScript/Reference/ Global_Objects/Date/getYear Date.prototype.getYear() Date.prototype.setYear()
51. @mybluewristband DEPRECATED Converts a date to a string, using Internet Greenwich Mean Time (GMT) conventions Exact format of the return value varies according to the platform and browser… https://developer.mozilla.org/en-US/ docs/Web/JavaScript/Reference/ Global_Objects/Date/toGMTString Date.prototype.toGMTString()
52. @mybluewristband NON STANDARD Converts a date to a string using the specified formatting Does not use Intl.DateTimeFormat Intl.DateTimeFormat formats dates in a standards-compliant way Deprecated as of Firefox 58+ Date.prototype.toLocaleFormat()
53. @mybluewristband MOMENT.JS A library! @mybluewristband
54. @mybluewristband ͳͥ
    MOMENT
55. @mybluewristband
56. @mybluewristband MORE GETTERS MOMENT.JS OFFERS moment().quarter() // Returns the year’s quarter moment().weekday() // Returns locale aware day of week moment().week() // Returns the week of the year moment().dayOfYear() // Returns the number day of the year from 1-366 moment().weeksInYear() // Returns the number of weeks in a specific year moment().unix() // Unix time in seconds
57. @mybluewristband DATE TIME MATH IS EASY 1-2-3 moment().add() // Add to any part(s) of a date moment().subtract() // Subtract from any part(s) of a date moment().startOf() // Sets any part of a date to the beginning moment().endOf() // Sets any part of a date to the end moment().local() // Set time to the local time zone moment().utc() // Set time to the equivalent UTC time zone moment().utcOffset() // Returns the UTC offset in minutes
58. @mybluewristband OMG TIMEZONES ⚠ ⚠ ⚠ ⚠ ⚠ ) vs & @mybluewristband
59. @mybluewristband
60. @mybluewristband Docs: https://momentjs.com/timezone/ Create moments with timezones Easily edit those timezones MOMENT TIMEZONE moment.tz() // Create a moment with a time zone or edit the timezone. moment.tz.Zone { name : 'America/Los_Angeles', // the unique identifier abbrs : ['PDT', 'PST'], // the abbreviations untils : [1414918800000, 1425808800000], // the timestamps in milliseconds offsets : [420, 480] // the offsets in minutes }
61. @mybluewristband SO, WHAT SHOULD WE USE? Θ͔Γ·ͤΜʜ
62. @mybluewristband
63. “ @mybluewristband Just use JavaScript until you can't anymore! Jennifer Wong
64. @mybluewristband You’ll
65. @mybluewristband BUT DON’T TAKE MY ADVICE Do what's best for your team and your need to scale @mybluewristband
66. @mybluewristband
67. @mybluewristband TEMPORAL A tc39 proposal
68. @mybluewristband
69. @mybluewristband
70. @mybluewristband ❤
71. @mybluewristband ϓϥεα
72. @mybluewristband Zell Liew for CSS Tricks!
74. @mybluewristband
75. @mybluewristband ͋Γ͕ͱ͏͟͝ ͍·ͨ͠ʂ ࣭໰ Jennifer Wong @mybluewristband https://github.com/jennz0r