“This is the sixth day of my participation in the Gwen Challenge in November. Check out the details: The Last Gwen Challenge in 2021.”

1. Prepare knowledge

  1. Escape character (\n,\f,\r,\t,\v)
  2. Multiline string
// Multi-line strings make use of escape characters
var string = 'i am \
liyilin\
';
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2. Create regular expressions

  1. literal
  2. new RegExp(“”, “igm”)

The regular expression defaults to greedy matching. If you don’t want greed to match, right?

3. The attribute

  1. I: Ignore case
  2. G: Global matching
  3. M: Multi-line matching

4. The expression

  1. [0-9]
  2. [a-z]
  3. [A-Z]
  4. [A-z]
  5. ^ : Put in the expression to represent not
  6. (\w)
Var reg = /(\w)\1/g; Var STR = 'aabbccdd'; str.match(reg) -- > ['aa', 'bb', 'cc', 'dd']Copy the code
  1. .=== [\r\n]

“| | BCD (ABC) a pipeline of Linux

5. Yuan character

  1. \w === [0-9A-z_]
  2. \W === [^\w]
  3. \d === [0-9]
  4. \D === [^\d]
  5. \s === whitespace character
  6. \S === [^\s]
  7. \ B: Match word boundaries
  8. \B: Match non-word boundaries

6. Quantifiers

  1. n+
  2. n*
  3. n? : n Occurs 0-1 times
  4. n{x}
  5. n{x,y}
  6. n{x,}
  7. ^n
  8. n$

7. Forward pre-check (assertion)

  1. ? = expression
  2. ? ! expression

This expression does not participate in selection, only in constraints

Method 8.

  1. RegExp
    1. Reg.test (STR): Returns true if STR matches successfully
    2. reg.exec(str)
        // If reg is a global match, exec performs like a seamless switch,
    // The cursor is lastIndex
    // If there is a subexpression in the reg, the value of the subexpression is returned for each match
    var reg = /(\w)\1(\w)\2/g;
	var str = 'aabbccdd';
	console.log(reg.exec(str)); 
	//["aabb", "a", "b"] -->lastIndex = 4
	console.log(reg.exec(str)); 
	//["ccdd", "c", "d"] -->lastIndex = 8
    console.log(reg.exec(str)); 
    //null -->lastIndex = 0
    
    //reg.lastIndex can be changed manually
    reg.lastIndex = 4;
    console.log(reg.exec(str));
	//["ccdd", "c", "d"] -->lastIndex = 8
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  2. String
    1. str.match(reg)


    Similar to exec, except that if reg is a global match, only all matches are returned, and no subexpression is returned. 2.str.search (erg)

    3. Str.split (reg)

    Return subexpression 4. Str.replace (reg,target)

    This is an outrageously powerful feature

       console.log(str.replace(reg, str));
   // The second $1 is the result of the subexpression 1
   console.log(str.replace(reg, "$1, $2");
   //
   console.log(str.replace(reg, function ($, $1) {
       return $1 + 'abc';
   })
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9.? : Does not capture groups

10. Qualifiers and locators

  1. qualifiers
  2. Localizers: Localizers do not match and cannot be used with qualifiers
    1. ^
    2. $
    3. (\ \ b b),

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