50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
|
|
# Special characters
|
|
|
|
As we've seen, a backslash `"\"` is used to denote character classes. So it's a special character.
|
|
|
|
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:[ \ ^ $ . | ? * + ( )`.
|
|
|
|
Don't try to remember it -- when we deal with each of them separately, you'll know it by heart automatically.
|
|
|
|
## Escaping
|
|
|
|
To use a special character as a regular one, prepend it with a backslash.
|
|
|
|
That's also called "escaping a character".
|
|
|
|
For instance, we need to find a dot `pattern:'.'`. In a regular expression a dot means "any character except a newline", so if we really mean "a dot", let's put a backslash before it: `pattern:\.`.
|
|
|
|
```js run
|
|
alert( "Chapter 5.1".match(/\d\.\d/) ); // 5.1
|
|
```
|
|
|
|
Brackets are also special characters, so if we want them, we should use `pattern:\(`. The example below looks for a string `"g()"`:
|
|
|
|
```js run
|
|
alert( "function g()".match(/g\(\)/) ); // "g()"
|
|
```
|
|
|
|
If we're looking for a backslash `\`, then we should double it:
|
|
|
|
```js run
|
|
alert( "1\2".match(/\\/) ); // '\'
|
|
```
|
|
|
|
## A slash
|
|
|
|
The slash symbol `'/'` is not a special character, but in Javascript it is used to open and close the regexp: `pattern:/...pattern.../`, so we should escape it too.
|
|
|
|
Here's what a search for a slash `'/'` looks like:
|
|
|
|
```js run
|
|
alert( "/".match(/\//) ); // '/'
|
|
```
|
|
|
|
From the other hand, the alternative `new RegExp` syntaxes does not require escaping it:
|
|
|
|
```js run
|
|
alert( "/".match(new RegExp()/\//) ); // '/'
|
|
```
|