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							3.9 KiB
						
					
					
				
			
		
		
	
	
							117 lines
						
					
					
						
							3.9 KiB
						
					
					
				# v2 Upgrade Guide
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## Common changes
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### Camel case naming schema
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Function submodules now use camelCase naming schema:
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```javascript
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// Before v2.0.0
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import differenceInCalendarISOYears from 'date-fns/difference_in_calendar_iso_years'
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// v2.0.0 onward
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import differenceInCalendarISOYears from 'date-fns/differenceInCalendarISOYears'
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```
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### New formatting tokens
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Starting with v2 `format` and `parse` uses [Unicode tokens].
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See [Unicode Tokens doc](./unicodeTokens.md) for more details.
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### String arguments
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Functions now don't accept strings as arguments. Strings should
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be parsed using `parseISO` (ISO 8601) or `parse`.
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See [this post](https://blog.date-fns.org/post/we-cut-date-fns-v2-minimal-build-size-down-to-300-bytes-and-now-its-the-smallest-date-library-18f2nvh2z0yal) for more details.
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```javascript
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// Before v2.0.0
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addDays('2016-01-01', 1)
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// v2.0.0 onward
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addDays(parseISO('2016-01-01'), 1)
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```
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### Arguments conversion
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All functions now implicitly convert arguments by following rules:
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|           | date         | number | string      | boolean |
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| --------- | ------------ | ------ | ----------- | ------- |
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| 0         | new Date(0)  | 0      | '0'         | false   |
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| '0'       | Invalid Date | 0      | '0'         | false   |
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| 1         | new Date(1)  | 1      | '1'         | true    |
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| '1'       | Invalid Date | 1      | '1'         | true    |
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| true      | Invalid Date | NaN    | 'true'      | true    |
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| false     | Invalid Date | NaN    | 'false'     | false   |
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| null      | Invalid Date | NaN    | 'null'      | false   |
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| undefined | Invalid Date | NaN    | 'undefined' | false   |
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| NaN       | Invalid Date | NaN    | 'NaN'       | false   |
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Notes:
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- as before, arguments expected to be `Date` are converted to `Date` using _date-fns'_ `toDate` function;
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- arguments expected to be numbers are converted to integer numbers using our custom `toInteger` implementation
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  (see [#765](https://github.com/date-fns/date-fns/pull/765));
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- arguments expected to be strings are converted to strings using JavaScript's `String` function;
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- arguments expected to be booleans are converted to boolean using JavaScript's `Boolean` function.
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`null` and `undefined` passed to optional arguments (i.e. properties of `options` argument)
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are ignored as if no argument was passed.
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If any argument is invalid (i.e. `NaN` for numbers and `Invalid Date` for dates),
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an invalid value will be returned:
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- `false` for functions that return booleans (expect `isValid`);
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- `Invalid Date` for functions that return dates;
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- `NaN` for functions that return numbers;
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- and `String('Invalid Date')` for functions that return strings.
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See tests and PRs [#460](https://github.com/date-fns/date-fns/pull/460) and
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[#765](https://github.com/date-fns/date-fns/pull/765) for exact behavior.
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### `null`
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`null` now is not a valid date. `isValid(null)` returns `false`;
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`toDate(null)` returns an invalid date. Since `toDate` is used internally
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by all the functions, operations over `null` will also return an invalid date.
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[See #537](https://github.com/date-fns/date-fns/issues/537) for the reasoning.
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### `RangeError`
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Functions now throw `RangeError` if optional values passed to `options`
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are not `undefined` or have expected values.
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This change is introduced for consistency with ECMAScript standard library which does the same.
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### `TypeError`
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All functions now check if the passed number of arguments is less
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than the number of required arguments and throw `TypeError` exception if so.
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### UMD/CDN
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The Bower & UMD/CDN package versions are no longer supported.
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### New locale format
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See [docs/Locale](https://date-fns.org/docs/Locale).
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Locales renamed:
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- `en` → `en-US`
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- `zh_cn` → `zh-CN`
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- `zh_tw` → `zh-TW`
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```javascript
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// Before v2.0.0
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import locale from 'date-fns/locale/zh_cn'
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// v2.0.0 onward
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import locale from 'date-fns/locale/zh-CN'
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```
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[unicode tokens]: https://www.unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
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