JavaScript regular expressions Discussion

JavaScript regular expressions

• A regular expression is a character sequence of search mode
• Search pattern can be used for text search and replace operation text

Using regular

String Methods

• In JavaScript, regular expression string often use two methods:
  • search()
  • replace()

Regular grammar

/[搜索模式]/[修饰符]

search()

• search () method to search for matching expression, but also to accept the search string as a parameter and returns the position matching .

Character search search ()

var str = "Huawei" ; 
var n = str.search("we");
// 返回 n = 3 

Regular use search ()

var str "Huawei" ;
var n = str.search(/we/i) ;
// 返回 n = 3

replace()

Character search replace ()

• All text after text replacement mode, return to replace the search mode

var str = "Huawei，China" ;
var re = str.replace("Huwawei","HUAWEI") ；
// 结果：HUAWEI,China!

Regular use replace ()

var str = "Huawei,China" ;
var re = str.replace(/huawei/i,"HUAWEI") ;
// 结果：HUAWEI,China!

Regular awareness

Regular expression modifiers

Modifiers	description
i	Not case sensitive
g	Perform a global search match (find all content)
m	The implementation of multi-line matching

Regular expression pattern

• expression

expression	description
[abc]	Find any character between the brackets
[0-9]	Find any number between 0-9
(X | y)	Find any options separated by a vertical bar

• Metacharacters

Metacharacters	description
\d	Find Digital
\s	Find a blank character
\b	Match a word boundary
\uxxxx	Find unicode character specified in hexadecimal xxx

• The definition of quantifiers

quantifier	description
n +	Matches any string comprising at least one of n
n *	Matches any string contains zero or more occurrences of n
n ？	Matches any zero or a string containing n

Using the test ()

• the Test () : a regular expression method

String to search through mode, and returns true or false

var re = /C/;
re.test("China - Huawei");
// 返回 true
/* 简单写 */
/C/.test("China - Huawei");

Use exec ()

• Exec () : a regular expression method

Search by specifying a search pattern string, and returns the searched text (not match returns to the Null)

var re = /C/ ; 
re.exec("China - Huawei");
// 返回 C
/*******简写*******/
/C/.exec("China - Huawei");