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This article mainly introduces what regular expressions and annotations are commonly used. It is very detailed and has a certain reference value. Friends who are interested must finish reading it.

Regular expressions are used in string processing, form verification and other occasions, practical and efficient. Some commonly used expressions are collected here for a rainy day.

Regular expressions that match Chinese characters: [\ u4e00 -\ u9fa5]

Note: matching Chinese is really a headache. It's easy to have this expression.

Match double-byte characters (including Chinese characters): [^\ X00 -\ xff]

Note: can be used to calculate the length of a string (a double-byte character length meter 2 ~ ~ ASCII character counter 1)

A regular expression that matches a blank line:\ n\ s*\ r

Comment: can be used to delete blank lines

Regular expression that matches the HTML tag:] * >. *? |

Commentary: the version circulated on the Internet is too bad, the above one can only match part of it, and there is still nothing I can do about complex nested tags.

Regular expression that matches the leading and trailing white space characters: ^\ s* |\ sblank $

Comment: a very useful expression that can be used to delete white space characters (including spaces, tabs, page feeds, etc.) at the beginning and end of a line

The regular expression that matches the Email address:\ W + ([- +.]\ w +) * @\ w + ([-.]\ w +) *.\ w + ([-.]\ w +) *

Comment: form validation is very useful

Regular expression that matches the URL URL: [a-zA-z] +: / / [^\ s] *

Note: the function of the version circulated on the Internet is very limited, and the above version can basically meet the needs.

Whether the matching account is legal (5-16 bytes are allowed at the beginning of the letter, and alphanumeric underscores are allowed): ^ [a-zA-Z] [a-zA-Z0-9 _] {4j 15} $

Comment: form validation is very useful

Match domestic phone number:\ d {3} -\ d {8} |\ d {4} -\ d {7}

Commentary: matching forms such as 0511-4405222 or 021-87888822

Match Tencent QQ number: [1-9] [0-9] {4,}

Commentary: Tencent QQ starts from 10000

Match the postcode of China: [1-9]\ d {5} (?!\ d)

Commentary: the postal code of China is 6 digits

Match ID:\ d {15} |\ d {18}

Commentary: Chinese ID cards are 15 or 18 digits

Match ip address:\ d +\.\ d +\.\ d +

Note: useful when extracting ip addresses

Match specific numbers:

^ [1-9]\ positive integer matching $/ /

^-[1-9]\ negative integer matching $/ /

^ -? [1-9]\ match integer

^ [1-9]\ d* | 0 $/ / matches a non-negative integer (positive integer + 0)

^-[1-9]\ d* | 0 $/ / matches non-positive integers (negative integers + 0)

^ [1-9]\ d *\.\ d * | 0\.\ d * [1-9]\ dfloat $/ / matches positive floating point numbers

^-([1-9]\ d *.\ d * | 0.\ d * [1-9]\ d *) $/ / matches negative floating point numbers

^ -? ([1-9]\ d *.\ d * | 0\.\ d * [1-9]\ d * | 0?\ .0 + | 0) $/ / match floating point number

^ [1-9]\ d *.\ d * | 0\.\ d * [1-9]\ d * | 0?\ .0 + | 0 $/ / matches non-negative floating point numbers (positive floating point number + 0)

^ (- ([1-9]\ d *\.\ d * | 0\.\ d * [1-9]\ d *)) | 0?\ .0 + | 0 $/ / matches non-positive floating point numbers (negative floating point + 0)

Commentary: useful when dealing with a large amount of data, pay attention to corrections in specific applications

Match a specific string:

^ [A-Za-z] + $/ / matches a string of 26 English letters

^ [Amurz] + $/ / matches a string of 26 English letters in uppercase

^ [amurz] + $/ / matches a string of 26 lowercase letters

^ [A-Za-z0-9] + $/ / matches a string of numbers and 26 letters

^\ w match $/ / match a string consisting of numbers, 26 letters, or underscores

The above is all the contents of the article "what are the Common regular expressions and annotations?" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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