JavaScript---Regular type (i)

Regular Expressions (regular expression) is an object that describes the character pattern . used to verify that the client's input data conforms to established rules , If we restrict the input character length or format, etc. . because client authentication , can save a lot of server-side system resources , and provide a better user experience .

① Creating regular expressions

two ways to create :

var box = newregexp (' box ', ' IG ');//first parameter optional string, second parameter pattern modifier var box =/box/ig;//directly with two backslashes

② Testing Regular Expressions

Test pattern match in string, return true or falsevar pattern =/box/i;var str = ' box '; alert (Pattern.test (str)); Use exec to return the matching array var pattern =/box/i;var str = ' box '; alert (pattern.exec (str));

③ Regular expression methods that use strings

/* Use the match method to get the matching array */var pattern =/box/ig;//Global search var str = ' This is abox! That's a box too! '; Alert (Str.match (pattern));//box,box, matching to two Boxalert (Str.match (pattern). length);//2, get array lengths/* Use Search to find matching data */ var pattern =/box/ig;//Global case-insensitive search. Notice that the search method finds the                       return, which means that G is dispensable. var str = ' This is abox! That's a box too! '; Alert (Str.search (pattern));//10, find the return position, or return-1/* Replace the matching data with replace */var pattern =/box/ig;var str = ' This is abox! That's a box too! Alert (Str.replace (pattern, Tom));//Replace Box with Tom

Run Results :

/* Use Split to split the string array */var pattern=//ig;var str = ' This is abox! That's a box too! '; Alert (str.split (pattern));//divide spaces into arrays

Run Results :

/* Use static property */var pattern =/(g) oogle/;var str = ' this isgoogle! '; Pattern.test (str); alert (regexp.input);//thisis Google!alert (Regexp.leftcontext);//thisisalert ( Regexp.rightcontext);//!alert (Regexp.lastmatch);//googlealert (Regexp.lastparen);//galert (RegExp.multiline);// False,ie is undefined.

/* Use dot character */varpattern =/g...gle/;//... Match three arbitrary characters var str = ' gooogle '; alert (Pattern.test (str));//true/* Use character class to match */var pattern =/g[a-za-z]*gle/;//[a-z]* Represents any of the characters in A-Z, is not case-sensitive, you can try to remove the changes in the [] see the effect var str = ' Google '; alert (Pattern.test (str));//true Varpattern =/g[^0-9]*gle /;//[^0-9]* denotes any non-0~9 character var str = ' go0gle '; alert (Pattern.test (str));//false var pattern =/[a-z][a-z]/;//[a-z] or [A-z] Any number of characters at the end with or without "+" no effect var str = ' GOOGLE '; alert (Pattern.test (str));//true/* Use meta-symbol to match */var pattern =/g\w*gle/;//\w* Matches any number of all alphanumeric and _var str = ' goo_gle '; alert (Pattern.test (str));//true var pattern =/\d{7,}/;//\d{7,} matches at least 7 non-numeric var str = ' Googlej '; alert (Pattern.test (str));//true

/* Use the anchor element character match */var pattern =/^google$/;//^ from scratch to match, starting at the end of the match var str = ' Google '; alert (Pattern.test (str));//true

/* Repeat match */var pattern =/g*gle/;//match 0~n var str = ' Google ',//*,?, +,{n,m}alert (pattern.test (str));//true

/* Use or pattern match */var pattern =/google|baidu|bing/;//google|baidu|bing three kinds of one of the string var str = ' Google '; alert (Pattern.test (str)) ;//true

JavaScript---Regular type (i)