The regular of JS

Concept: Regular Expressions: Use some special symbols (characters) to represent specific content to find and match a string that matches a rule.

The definition of a regular expression:

1 Direct definition / Regular expression is content /[modifier] Recommended use Eg:var reg=/\d/g

2 object definition var reg=new RegExp (string, modifier)

Two escape characters

\d Digital

\d Non-digital

\s Spaces

\s Non-whitespace

\w numbers, letters, underscores

\w non-numeric, non-alphabetic, non-underlined

\b The boundaries of words, independent parts (starting position, end position, space)

\b Part of the non-boundary

    . Any one character

\. The real point

Three classifiers

+ {1,} Repeat at least 1 times, up to No limit

? {0,1} repeats at least 0 times and repeats up to 1 times

* {0,} Repeat at least 0 times, up to No limit

{n,} repeats at least n times, up to No limit

{n,m} repeats at least n times and repeats up to M times

| or eg:a|b.

^ Match start

$ match End

[] matches any one of the characters in the brackets, representing any one character [A-z] between one character [1-9] 1-9 and any letter [a-z] A-Z any letter

[^1-2] Take the anti-exclusion number

Four matching Chinese

[\U4E00-\U9FA5] any of the Chinese characters

Five methods

1 Test

To see if the regular matches the specified string

Syntax: regular. Test ("string")

Return value: True success

False failed

1 var str="xubj"; 2 // true 3 // false

2 Search Find the location of the first occurrence of a matching string

String. Search (string or/Regular/)

return value:

Find the return subscript

Return not found-1

var str="nihaoxubj"; Console.log (Str.search ("i ")); // 1 return subscript console.log (Str.search (/\d/g)); // -1 not found return-1

3 match matches a string or regular, placing the matched result in an array

Syntax string. Match (string or regular)

return value:

Finds the returned array of results found

Null not Found

var str="xubjsdsfdsxubjsd25"; Console.log (Str.match (// ["Xubj", index:0, Input: "XUBJSDSFDSXUBJSD25"] // ["Xubj", "XUBJ"] // NULL

4 Replace replaces the match to the string

Syntax string. replace (string or regular, string or function)

Return value: The new string after substitution, the original string is unchanged

Note: The second argument is a function, it must have a return value, otherwise it will replace the original content with undefined

varStr="XUBJ"; Console.log (Str.replace (/x/,0));//0UBJ Returns the changed stringConsole.log (str);//xubj Original string unchangedvarNewstr=str.replace (/x/, function () {return 'F';}); Console.log (NEWSTR);//FUBJvarNewstr1=str.replace (/x/,function ($0,$1,$2) {Console.log ($0,$1,$2);//x 0 xubj    /*parameter 1 to match content, same as the first parameter of replace parameter 2 matches the location of the corresponding position subscript parameter 3 the original string*/});//example to turn x in a string into a *varStr="XUBJNIHAOXUBJ";varNewstr2=str.replace (/xu/g,function ($0,$1,$2){     varStr="";  for(varI=0; i<$0. length;i++) {str+="*"; }     returnstr;}); Console.log (NEWSTR2); //**BJNIHAO**BJ

Two groups and children

Group with ()

The child is placed in parentheses, and each parenthesis can be considered a child

Replace method matches Subkeys

Parameter starts with the second one, and corresponds to each child

//Replace method matches subkeysvarreg=/(\d+) (-)/G;varStr="2017-12-08";varNewstr=str.replace (Reg,function ($0,$1,$2){    //Console.log ($);//2017-12-Same as the contents of the regular (to match the content)//Console.log ($);//2017 12 content in the first group//Console.log ($);//--content in the second group    return$1+'/';}); Console.log (NEWSTR); //2017/12/08

Match method matches subkey

There are no children in the array returned by G

There are no children in the array returned by G

// Match method matches subkey var str="xubj"; Console.log (Str.match (//["Xubj", "Xu", "B", "J"] no G returns the subkey Console.log (Str.match (/(Xu) (b) (j)/g)); // ["XUBJ"]  has G does not return children

//formatted Datevard1="2017-12-08";varD2="2017+++12++++08";vard3="2017////12//08";vard4="2017+---12+++-08";//Explain a bunch of numbers a bunch of non-numbers a bunch of numbers a bunch of non-numbers a bunch of numbersvarreg=/(\d+) \d+ (\d+) \d+ (\d+)/;varNewstr=d1.replace (Reg,function ($0,$1,$2,$3){    //$1,$2,$3 represents children in a group    return$1+'years'+$2+'Month'+$3+'Day';});

The regular of JS