Update regexp basic cheatsheets (#906)

regexp.md

@@ -1,12 +1,59 @@
 ---
-title: Regexp
+title: regexp
+category: Others
+layout: 2017/sheet
+weight: -1
+authors:
+  - github: rizqyhi
+updated: 2018-10-26
+description: |
+  Basic cheatsheets for regular expression
 ---
 
-    (?P<named_match>...)
+### Character Classes
-    (?:invisible group)
 
-    (?!negative look-ahead)
+| Pattern | Description |
-    (?=positive look-ahead)
+| ---     | --- |
-    (?<!negative look-behind)
+| `.`     | Any character, except newline |
-    (?<=positive look-behind)
+| `\w`    | Word |
+| `\d`    | Digit |
+| `\s`    | Whitespace |
+| `\W`    | Not word |
+| `\d`    | Not digit |
+| `\S`    | Not whitespace |
+| `[abc]` | Any of a, b, or c |
+| `[a-e]` | Characters between `a` and `g` |
+| `[1-9]` | Digit between `1` and `9` |
 
+### Anchors
+
+| Pattern | Description |
+| ---     | --- |
+| `^abc` | Start with `abc` |
+| `abc$` | End with `abc` |
+
+### Escaped Characters
+
+| Pattern | Description |
+| ---        | --- |
+| `\. \* \\` | Escape special character used by regex |
+| `\t`       | Tab |
+| `\n`       | Newline |
+| `\r`       | Carriage return |
+
+### Groups
+
+| Pattern | Description |
+| ---     | --- |
+| `(abc)` | Capture group |
+
+### Quantifiers
+
+| Pattern  | Description |
+| ---      | --- |
+| `a*`     | Match 0 or more |
+| `a+`     | Match 1 or more |
+| `a?`     | Match 0 or 1 |
+| `a{5}`   | Match exactly 5 |
+| `a{3,}`  | Match 3 or more |
+| `a{1,3}` | Match between 1 and 3 |