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This article introduces the knowledge of "introduction to regular expressions of javascript". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Overview

A regular expression is a pre-declared set of rules that match characters in a string.

Basic grammar

Metacharacter

In the pattern of regular expressions, some characters have a special meaning and are called metacharacters. Metacharacters are matched against a single character.

\ w matches uppercase and lowercase English characters and any number between 0 and 9 and underscores, which is equivalent to [a-zA-Z0-9]

\ W does not match uppercase and lowercase English characters and any number between 0 and 9, which is equivalent to [^ a-zA-Z0-9]

\ s matches any white space character, which is equivalent to [\ f\ n\ r\ t\ v]

\ s matches any non-white space character, which is equivalent to [^\ s]

\ d matches any single number between 0 and 9, equivalent to [0 # 9]

\ d does not match any single number between 0 and 9, equivalent to [^ 0 # 9]

[\ u4e00 -\ u9fa5] matches any single Chinese character (here Unicode code is used to represent Chinese characters)

Delimiter

The more general regular expression delimiter is double slash / regex/

The concept of atoms

Atoms in regular expressions are divided into visible and invisible atoms.

[\ f\ n\ r\ t\ v] belongs to invisible atoms, others represent visible atoms

Quantifier

\ * match 0 to multiple metacharacters, equivalent to {0,}

? Matches 0 to 1 metacharacters, which is equivalent to {0jin1}

{n} matches n metacharacters

{n,} matches at least n metacharacters

{nrecoery m} matches n to m metacharacters

\ + match at least 1 metacharacter, equivalent to {1,}

Boundary

\ b match word boundaries

The ^ string must start with the specified character

The $string must end with the specified character

Capture packet

In regular expressions, several units (which can be characters, regular expressions) are organized together to form a separate unit using ().

In regular expressions, packets are divided into capture packets and non-capture packets.

/ (pattern) / flags

Mode correction

Greed / laziness, ignore case, ignore white space characters

Working with scen

Form validation, template engine

This is the end of the introduction to javascript's regular expressions. Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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