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Copy file name to clipboardExpand all lines: 9-regular-expressions/06-regexp-boundary/article.md
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@@ -25,29 +25,28 @@ So, it matches the pattern `pattern:\bHello\b`, because:
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1. At the beginning of the string matches the first test `pattern:\b`.
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2. Then matches the word `pattern:Hello`.
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3. Then the test `pattern:\b`- matches again, as we're between `subject:o` and a space.
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3. Then the test `pattern:\b` matches again, as we're between `subject:o` and a space.
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Шаблон `pattern:\bJava\b`также совпадёт. Но не`pattern:\bHell\b` (потому что после `subject:l` нет границы слова), и не `pattern:Java!\b` (восклицательный знак не является "символом слова" `pattern:\w`, поэтому после него нет границы слова).
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The pattern `pattern:\bJava\b`would also match. But not`pattern:\bHell\b` (because there's no word boundary after `l`) and not `Java!\b` (because the exclamation sign is not a wordly character `pattern:\w`, so there's no word boundary after it).
alert( "Hello, Java!".match(/\bHell\b/) ); // null (no match)
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alert( "Hello, Java!".match(/\bJava!\b/) ); // null (no match)
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```
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Так как `pattern:\b`является проверкой, то не добавляет символ после границы к результату.
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We can use `pattern:\b`not only with words, but with digits as well.
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Мы можем использовать `pattern:\b` не только со словами, но и с цифрами.
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Например, регулярное выражение `pattern:\b\d\d\b` ищет отдельно стоящие двузначные числа. Другими словами, оно требует, чтобы до и после `pattern:\d\d` был символ, отличный от `pattern:\w` (или начало/конец строки)
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For example, the pattern `pattern:\b\d\d\b` looks for standalone 2-digit numbers. In other words, it looks for 2-digit numbers that are surrounded by characters different from `pattern:\w`, such as spaces or punctuation (or text start/end).
```warn header="Граница слова`pattern:\b`не работает для алфавитов, не основанных на латинице"
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Проверка границы слова `pattern:\b`проверяет границу, должно быть `pattern:\w`с одной стороны и "не`pattern:\w`" - с другой.
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```warn header="Word boundary`pattern:\b`doesn't work for non-latin alphabets"
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The word boundary test `pattern:\b`checks that there should be `pattern:\w`on the one side from the position and "not`pattern:\w`" - on the other side.
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Но`pattern:\w`означает латинскую букву (или цифру или знак подчёркивания), поэтому проверка не будет работать для других символов (например, кириллицы или иероглифов).
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But`pattern:\w`means a latin letter `a-z` (or a digit or an underscore), so the test doesn't work for other characters, e.g. cyrillic letters or hieroglyphs.
Copy file name to clipboardExpand all lines: 9-regular-expressions/07-regexp-escaping/article.md
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# Escaping, special characters
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As we've seen, a backslash `"\"` is used to denote character classes. So it's a special character in regexps (just like in a regular string).
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As we've seen, a backslash `pattern:\` is used to denote character classes, e.g. `pattern:\d`. So it's a special character in regexps (just like in regular strings).
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There are other special characters as well, that have special meaning in a regexp. They are used to do more powerful searches. Here's a full list of them: `pattern:[ \ ^ $ . | ? * + ( )`.
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Don't try to remember the list -- soon we'll deal with each of them separately and you'll know them by heart automatically.
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## Escaping
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Let's say we want to find a dot literally. Not "any character", but just a dot.
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Let's say we want to find literally a dot. Not "any character", but just a dot.
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To use a special character as a regular one, prepend it with a backslash: `pattern:\.`.
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alert( "/".match(/\//) ); // '/'
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```
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On the other hand, if we're not using `/.../`, but create a regexp using `new RegExp`, then we don't need to escape it:
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On the other hand, if we're not using `pattern:/.../`, but create a regexp using `new RegExp`, then we don't need to escape it:
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```js run
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alert( "/".match(newRegExp("/")) ); //'/'
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```
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alert( "/".match(newRegExp("/")) ); //finds /
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```
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## new RegExp
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alert( "Chapter 5.1".match(reg) ); // null
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```
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The search worked with `pattern:/\d\.\d/`, but with `new RegExp("\d\.\d")` it doesn't work, why?
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The similar search in one of previous examples worked with `pattern:/\d\.\d/`, but `new RegExp("\d\.\d")` doesn't work, why?
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The reason is that backslashes are "consumed" by a string. Remember, regular strings have their own special characters like`\n`, and a backslash is used for escaping.
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The reason is that backslashes are "consumed" by a string. As we may recall, regular strings have their own special characters, such as`\n`, and a backslash is used for escaping.
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Please, take a look, what "\d\.\d" really is:
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Here's how "\d\.\d" is preceived:
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```js run
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alert("\d\.\d"); // d.d
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```
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The quotes "consume" backslashes and interpret them, for instance:
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String quotes "consume" backslashes and interpret them on their own, for instance:
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-`\n` -- becomes a newline character,
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-`\u1234` -- becomes the Unicode character with such code,
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- ...And when there's no special meaning: like `pattern:\d` or `\z`, then the backslash is simply removed.
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So the call to `new RegExp` gets a string without backslashes. That's why the search doesn't work!
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So `new RegExp` gets a string without backslashes. That's why the search doesn't work!
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To fix it, we need to double backslashes, because quotes turn `\\` into `\`:
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To fix it, we need to double backslashes, because string quotes turn `\\` into `\`:
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