JavaScript Basics -10 JavaScript Regular Expressions (overview, defining Regular, RegExp objects, string methods for pattern matching)

First, JavaScript Regular expression overview

Regular Expressions Overview

-Regular Expressions (Regular expression): Expressions that are composed of ordinary characters and special characters that describe a particular character rule

-Regular expressions are often used to search, match, or replace specific forms of text in a text. such as: Word frequency statistics, verify whether the string conforms to the message format, block a post of the restrictive words, etc.

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The initial experience of regular expressions

-Verify that the phone format entered by the user is legal

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Second, JavaScript defines regular expressions

Normal characters

-All individual uppercase and lowercase letters, numbers are a regular expression that matches a single character, which is the same as itself. Such as:

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-some characters in regular expressions have special grammatical meanings and cannot be used directly, and must be escaped with \ to be used

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Character

-Regular Expressions match a range of characters using the following syntax

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Pre-defined character set

-The following meta-character references can be used in regular expressions to simplify

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Quantity words

-A regular expression can use the following special characters to define the frequency of occurrences of a character---quantifier metacharacters

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Select and group

-Regular expressions use the following syntax to define sub-expressions grouping or selecting

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Specify a matching location

-You can use the following characters to match a specified position

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Third, JavaScript RegExp object

Create a RegExp object

-There are two methods of creating a regular expression object:

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Properties of the REGEXP

-The RegExp object has the following properties:

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Methods of REGEXP

-The RegExp object has the following methods

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Iv. JavaScript string method for pattern matching

Replace method

-Strobject.replace (Substring/regexp,replacement)

-Replaces a substring of a particular format in a string, returning the replaced result

-the first parameter can be either a fixed substring or a regular expression object

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Match method

-Strobject.match (SUBSTRING/REGEXP)

-Returns the match of one or more substrings/regular expressions

-Similar to the indexof () method, but it returns the matching value instead of the subscript that matches the string

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Search method

-Strobject.search (RegExp)

-Returns a subscript that matches the specified regular expression string for the first time, and returns 1 if no match is present

-Similar to indexof (), but indexof () does not support regular expressions

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Split method

-Strobject.split (Str/regexp,[howmany])

-Splits the original string with a specified string or regular expression, returning the array of substrings that were split

-If the Howmany attribute is specified, only the first howmany substring is returned

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Summary: This chapter covers JavaScript regular expressions (overview of regular expressions, defining regular expressions, RegExp objects, string methods for pattern matching)

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JavaScript Basics -10 JavaScript Regular Expressions (overview, defining Regular, RegExp objects, string methods for pattern matching)