"JS" about regular expressions

The regular expression describes the pattern object of the character

Grammar:

var patt=New  RegExp (pattern,modifiers); or the simpler way var patt=/pattern/modifiers;

• The pattern describes an expression model.
• The modifier (modifiers) describes whether the retrieval is global, case sensitive, and so on.

　　Note: When you use constructors to create regular objects, you need a regular character escaping rule (preceded by a backslash \). For example, the following are equivalent:

        var New REGEXP ("\\w+");         var re =/\w+/;   

• Regular expression modifiers
  • The i -modifier is used to perform a case-insensitive match.
  • The g -modifier is used to perform a full-text search (instead of finding the first one to stop looking, but to find all matches).
• Method:
  • The test () method searches for the value specified by the string, depending on the result and returns TRUE or false.
    

    var patt1=New RegExp ("E");d ocument.write (Patt1.test ("The best things on life is Free"); True

  • The EXEC () method retrieves the specified value in the string. The return value is the value that was found. If no match is found, NULL is returned.
    

    var patt1=New RegExp ("E");d ocument.write (Patt1.exec ("The best things on life is Free");    //e

• modifier: modifier is used to perform case-sensitive and global matching
  

  modifier	description
  I	performs a match that is case insensitive.
  G	performs a global match (finds all matches rather than stops after the first match is found).
  m	performs multi-line matching.

  
  
  
• Square brackets: square brackets are used to find characters in a range:
  

  An expression	Description
  [ABC]	Look for any characters between square brackets.
  [^ABC]	Look for any characters that are not in square brackets.
  [0-9]	Look for any number from 0 to 9.
  [A-z]	Finds any characters from a to lowercase z from a small write.
  [A-z]	Look for any characters from uppercase A to uppercase Z.
  [A-z]	Look for any characters from uppercase A to lowercase z.
  [ADGK]	Finds any character within a given collection.
  [^ADGK]	Finds any character outside the given collection.
  (Red|blue|green)	Finds any of the specified options.

• metacharacters: meta-character (Metacharacter) is a character with a special meaning:
  The

  metacharacters	description
  .	finds a single character, in addition to line breaks and line terminators.
  \w	to find word characters.
  \w	to find non-word characters.
  \d	to find numbers.
  \d	to find non-numeric characters.
  \s	to find white space characters.
  \s	to find non-whitespace characters.
  \b	matches the word boundary.
  \b	matches non-word boundaries.
  \	find NUL characters.
  \ n	find line breaks.
  \f	Find a page break.
  \ r	find a carriage return.
  \ t	find tabs.
  \v	to find vertical tabs.
  \xxx	to find characters that are specified in octal number XXX.
  \xdd	to find the characters specified in hexadecimal digits dd.
  \uxxxx	finds Unicode characters that are specified in hexadecimal number xxxx.

• quantifier td> matches any string that contains at least one n. The

  quantifier	description
  n+
  n	matches any string containing 0 or more n.
  n?	matches any string that contains 0 or one n.
  n{x}	matches a string containing a sequence of X N.
  n{x,y}	matches a string containing a sequence of X or Y N.
  n{x,}	matches a string containing a sequence of at least X N.
  n$	matches any string that ends with N.
  ^n	matches any string that begins with N.
  ? =n	matches any string immediately followed by the specified string n.
  ?! n	matches any string that is not followed by the specified string n.

• RegExp Object Method

  method	Description	FF	ie
  compile	compiles the regular expression.	1	4
  exec	Retrieves the value specified in the string. Returns the found value and determines its location.	1	4
  Test	Retrieves the value specified in the string. Returns TRUE or FALSE.	1	4

  About compile method:
  • Feature Description: This method compiles the specified regular expression, and the compiled regular expression The line speed will increase, and if the regular expression is called more than once, then calling the compile method can effectively increase the execution speed of the code and will not have a noticeable effect if the regular expression can only be used once.  
  • basic syntax: Objreg.compile (Pattern[,flag])  
    • objreg required option, regexp object variable name  
    • Pat Tern Mandatory option Regular expression
    • flag option matching option. Optional combinations are:
      • g (Global Search)
      • I (ignoring case)
      • m (Multi-line search)

  • Using the Compile method can also modify and recompile a specified regular expression to improve the adaptability of regular expressions!
    

• A String object method that supports regular expressions

  Method	Description	FF	IE
  Search	Retrieves a value that matches a regular expression.	1	4
  Match	Finds a match for one or more regular expressions.	1	4
  Replace	Replace the substring that matches the regular expression.	1	4
  Split	Splits a string into an array of strings.	1	4

Reference:

JavaScript REGEXP Objects

JavaScript RegExp Object reference manual

Compile method (regular expression) (JavaScript)

"JS" about regular expressions