86 lines
3.9 KiB
Markdown
86 lines
3.9 KiB
Markdown
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# Unicode character properties \p
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[Unicode](https://en.wikipedia.org/wiki/Unicode), the encoding format used by JavaScript strings, has a lot of properties for different characters (or, technically, code points). They describe which "categories" character belongs to, and a variety of technical details.
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In regular expressions these can be set by `\p{…}`. And there must be flag `'u'`.
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For instance, `\p{Letter}` denotes a letter in any of language. We can also use `\p{L}`, as `L` is an alias of `Letter`, there are shorter aliases for almost every property.
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Here's the main tree of properties:
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- Letter `L`:
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- lowercase `Ll`, modifier `Lm`, titlecase `Lt`, uppercase `Lu`, other `Lo`
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- Number `N`:
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- decimal digit `Nd`, letter number `Nl`, other `No`
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- Punctuation `P`:
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- connector `Pc`, dash `Pd`, initial quote `Pi`, final quote `Pf`, open `Ps`, close `Pe`, other `Po`
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- Mark `M` (accents etc):
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- spacing combining `Mc`, enclosing `Me`, non-spacing `Mn`
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- Symbol `S`:
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- currency `Sc`, modifier `Sk`, math `Sm`, other `So`
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- Separator `Z`:
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- line `Zl`, paragraph `Zp`, space `Zs`
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- Other `C`:
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- control `Cc`, format `Cf`, not assigned `Cn`, private use `Co`, surrogate `Cs`
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```smart header="More information"
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Interested to see which characters belong to a property? There's a tool at <http://cldr.unicode.org/unicode-utilities/list-unicodeset> for that.
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You could also explore properties at [Character Property Index](http://unicode.org/cldr/utility/properties.jsp).
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For the full Unicode Character Database in text format (along with all properties), see <https://www.unicode.org/Public/UCD/latest/ucd/>.
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```
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There are also other derived categories, like:
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- `Alphabetic` (`Alpha`), includes Letters `L`, plus letter numbers `Nl` (e.g. roman numbers Ⅻ), plus some other symbols `Other_Alphabetic` (`OAltpa`).
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- `Hex_Digit` includes hexadecimal digits: `0-9`, `a-f`.
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- ...Unicode is a big beast, it includes a lot of properties.
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For instance, let's look for a 6-digit hex number:
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```js run
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let reg = /\p{Hex_Digit}{6}/u; // flag 'u' is required
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alert("color: #123ABC".match(reg)); // 123ABC
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```
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There are also properties with a value. For instance, Unicode "Script" (a writing system) can be Cyrillic, Greek, Arabic, Han (Chinese) etc, the [list is long]("https://en.wikipedia.org/wiki/Script_(Unicode)").
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To search for characters in certain scripts ("alphabets"), we should supply `Script=<value>`, e.g. to search for cyrillic letters: `\p{sc=Cyrillic}`, for Chinese glyphs: `\p{sc=Han}`, etc:
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```js run
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let regexp = /\p{sc=Han}+/gu; // get chinese words
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let str = `Hello Привет 你好 123_456`;
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alert( str.match(regexp) ); // 你好
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```
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## Building multi-language \w
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The pattern `pattern:\w` means "wordly characters", but doesn't work for languages that use non-Latin alphabets, such as Cyrillic and others. It's just a shorthand for `[a-zA-Z0-9_]`, so `pattern:\w+` won't find any Chinese words etc.
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Let's make a "universal" regexp, that looks for wordly characters in any language. That's easy to do using Unicode properties:
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```js
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/[\p{Alphabetic}\p{Mark}\p{Decimal_Number}\p{Connector_Punctuation}\p{Join_Control}]/u
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```
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Let's decipher. Just as `pattern:\w` is the same as `pattern:[a-zA-Z0-9_]`, we're making a set of our own, that includes:
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- `Alphabetic` for letters,
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- `Mark` for accents, as in Unicode accents may be represented by separate code points,
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- `Decimal_Number` for numbers,
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- `Connector_Punctuation` for the `'_'` character and alike,
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- `Join_Control` -– two special code points with hex codes `200c` and `200d`, used in ligatures e.g. in arabic.
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Or, if we replace long names with aliases (a list of aliases [here](https://www.unicode.org/Public/UCD/latest/ucd/PropertyValueAliases.txt)):
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```js run
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let regexp = /([\p{Alpha}\p{M}\p{Nd}\p{Pc}\p{Join_C}]+)/gu;
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let str = `Hello Привет 你好 123_456`;
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alert( str.match(regexp) ); // Hello,Привет,你好,123_456
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```
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