Introduction to Regular Expression Test Tool
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The role of regular expressions
Regular Expression (Regular Expression) is a text pattern, including ordinary characters (for example, a to z between the letters) and special characters (known as "metacharacters"). Regular expressions use a single string to describe, and match, a series of strings that match a syntax rule. Regular expressions are tedious, but they are powerful, and learning to use them will give you a sense of accomplishment in addition to efficiency. Many programming languages support string manipulation using regular expressions.
Commonly used metacharacters| Code | Description |
|---|
| . | Match any character except line breaks |
| \w | Match letters or numbers or underscores |
| \s | Matches any white space character |
| \d | Matches a number |
| \b | Matches the beginning or end of a word |
| ^ | Matches the beginning of a string |
| $ | Matches the end of a string |
Common Qualifiers| Code/Syntax | Description |
|---|
| * | Repeat zero or more times |
| + | Repeat once or more |
| ? | Repeat zero or one time |
| {n} | Repeat n times |
| {n,} | Repeat n or more times |
| {n,m} | Repeat n to m times |
Common Antonyms| Code/Syntax | Description |
|---|
| \W | Match any character that is not a letter, number, underscore, or Chinese character. |
| \S | Match any character that is not a blank character |
| \D | Match any character that is not a number |
| \B | Match any character that is not the beginning or end of a word. |
| [^x] | Match any character except x |
| [^aeiou] | Matches any character except aeiou. |
Regular Expressions Reference
| Characters | Description |
|---|
| ^\d+$ | //match non-negative integer (positive integer + 0) |
| //Match integer ^\d+(\. \d+)? \d+(\...\d+)? | //Match non-negative floating point numbers (positive floats + 0) |
| ^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*))$ | //Match positive floating point numbers |
| ^((-\d+(\.\d+)?)|(0+(\.0+)?))$ | //Match non-negative floats (negative floats + 0) |
| ^(-(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*)))$ | //match negative float |
| ^(-?\d+)(\.\d+)?$ | //Match floating point numbers |
| ^[A-Za-z]+$????????? | //Match a string of 26 letters of the alphabet |
| ^[A-Z]+$ ??? | //matches a string of 26 uppercase letters of the alphabet |
| ^[a-z]+$ | //Match strings consisting of 26 letters in lower case |
| ^[A-Za-z0-9]+$ | //Match strings consisting of numbers and 26 letters of the alphabet |
| ^\w+$ | //Match strings consisting of numbers, 26 letters or underscores. |
| ^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$ | //Match email address |
| ^[a-zA-z]+://match (\w+(-\w+)*)(\. (\w+(-\w+)*))*(\? \S*)? $ | //Match url |
| [\u4e00-\u9fa5] | Regular expression to match Chinese characters |
| [^\x00-\xff] | Match double-byte characters (including Chinese characters) |
| \n[\s| ]*\r | Regular expression to match blank lines |
| /<(.*)>.*<\/>|<(.*)\/>/ | Regular expression to match HTML tags |
| (^\s*)|(\s*$) | Regular expression to match first and last spaces |
| \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)* | Regular expression to match Email address |
| ^[a-zA-z]+://(\w+(-\w+)*)(\.(\w+(-\w+)*))*(\?\S*)?$ | Regular expression to match URL of web site |
| ^[a-zA-Z][a-zA-Z0-9_]{4,15}$ | Match the account number is legal (start with a letter, allow 5-16 bytes, allow alphanumeric underscore) |
| (\d{3}-|\d{4}-)?(\d{8}|\d{7})? | Match Domestic Phone Number |
| ^[1-9]*[1-9][0-9]*$ | Match Tencent QQ number |