Regular Expressions Daily collection collation (simple and practical) _ Regular expressions

Regular expressions, also known as formal representations, general representations. (English: Regular Expression, often abbreviated as regex, RegExp, or re) in code, a concept of computer science. A regular expression uses a single string to describe and match a sequence of rules that conform to a certain syntactic rule. In many text editors, regular expressions are often used to retrieve and replace text that conforms to a pattern.

The function of the regular expression is very powerful, the nonsense does not say much, give everybody to share the content of the reorganization directly.

One: basic matching characters:

\d matching number eg: ' 5\d0 '-------> ' 580 '

\w matching letters or numbers eg: ' \d\w\w '---------> ' 8zh '

. Matches any character except a newline character, eg: ' en. '-----------> ' zh& '

\s whitespace character (tab) or space

Two: Match character length:

* represents any character (including 0)

+ represents at least one character

? Represents 0 or 1 characters

{n} represents n characters

{N,m} represents n-m characters

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Exercises together: \d{3}\s+\d{3,8};

The answer here is 2333: The match is made up of 3 digits immediately followed by at least one space or a blank character immediately following 3 to 8 digits;

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<<<<< added: "Such special characters as '-' need to be translated in order to match oh like this ' \-' >>>>>

Three: But if this is a simple match, it's a little bit simpler, and we need more accurate matching methods for complex matches:

[0-9a-za-z\_] can match a number or a letter or an underscore, the test: ' 0 ', ' a ', ' Z ', ' _ ' can match, so that the expression of the medium is a possible or can be the composition of the way;

[0-9a-za-z\_]+ can match a string consisting of at least one number or letter or underscore;

[A-za-z\_] [0-9a-za-z\_]* can match the beginning of a letter or underscore followed by any number or letter or underscore;

[A-za-z\_] [0-9a-za-z\_] {0,19} limit length of 1 to 20, why 1 to 20, the beginning of a bit immediately after the string limit to 0 to 19, so the maximum length limit in 20;

a| B can match A or b. [J|j]aina can match Jaina or Jaina;

^ expression must begin with a character, eg: ^\d must begin with a number

$ means must end with a character, eg: \d$ must end with a number, notice the way they are expressed ^ is placed in front of the character, $ is placed behind the character

Four: JS in the verification method:

var reg= ' \d{3}\s+\d{3,8} ';
var tel= ' 010 123456 ';
Console.log (Reg.test (tel));//true

The above is a small series to introduce regular expression of routine collection (simple and practical), hope to help everyone, if you have any questions please give me a message, small series will promptly reply to everyone. Here also thank you very much for the cloud Habitat Community website support!