Js regular functions (internal)

1) String method a.) String. search () parameter: it can be a regular expression or a normal String. Returned value: If a match is found, the index location of the first character is returned. If no match is found, the return value is-1 vars & quot; Helloworld. & quot; reg/world/I; // I indicates no size difference... syntax 1 .) string Method
A.) String. search ()
Parameter: it can be a regular expression or a normal string.
Returned value: If a match is found, the index location of the first character is returned. If no match is found,-1 is returned.
Var s = "Hello world .";
Reg =/world/I; // I indicates case insensitive
Alert (s. search (reg ));
B.) String. replace ()
Parameter: 1. Regular Expression 2. string used for replacement
Returns the replaced string.
Var s = "Hello world. World! ";
Reg =/world/gi; // g is in global mode and all matches are replaced.
Alert (s. replace (reg, 'A '));
Subexpression (the matching subexpression in brackets can be accessed through $ n ):
Var s = "11 22 33 44 55 66 77! ";
Reg =/(\ S +) (\ s +) (\ S +)/g; // I indicates case insensitive
Alert (s. replace (reg, '$3 $2 $ 1'); // 22 11 44 33 66 44 77!
C.) String. match ()
Put the matched string in the array and return it. If no match exists, null is returned.
// In global mode, each match is placed in the returned array.
Var s = "My phone number is 0631-1234567. Your phone number is 021-87654321. We often contact you! ";
Reg =/(0 \ d-\ d {8} | 0 \ d-\ d {7})/g; // note that this regular expression may be incomplete and may be easier to write.
Alert (s. match (reg); // 0631-1234567,021-87654321
// If no g tag is set, the returned array [0] is the overall match, and 1-N indicates the child match.
Var s = "My salary is $800, and her salary is $400! ";
Reg =/(\ $) (\ d +)/; // $ escape is required
Alert (s. match (reg); // $800, $, 800
D.) String. split ([delimiter [, limit on the number of returned elements])
// Common Segmentation
Var s = "My salary is $800, and her salary is $400! ";
Alert (s. split (',') [0]); // my salary is $800
// Use regular expressions
Var s = "China's population reaches 1.4 billion, but its per capita income is less than 3000 US dollars. Therefore, China is still in developing countries! ";
Alert (s. split (/\ d/); // China has a population of hundreds of millions, but its per capita income is less than USD, So China is still in a developing country!
2.) RegExp object
A.) RegExp. test (str)
Why? If tr matches this regular object, true is returned.
Var s = "This statement contains the number 123 for testing! ";
Var re =/\ d + /;
If (re. test (s ))
Alert ("contains numbers ");
B .w.regexp.exe c () is more powerful than String. match ().
// Non-Global exec, [0] returns a match, 1-N returns a child match
Var s = "number 123, letter abc, underline _! ";
Var re =/(\ w) \ w */;
Alert(re.exe c (s); // 123,1
Alert(re.exe c (s). input); // number 123, letter abc, underline _!
Alert(re.exe c (s). index); // 2
// With global tag
Var s = "number 123, letter abc, underline _! ";
Var re =/(\ w) \ w */g;
Alert (re. lastIndex); // 0
Alert(re.exe c (s); // 123,1
Alert (re. lastIndex); // 5
Alert(re.exe c (s); // abc,
Alert (re. lastIndex); // 11
Alert(re.exe c (s ));//_,_
Alert (re. lastIndex); // 16
C.) Regular Expression Constructor
Re = new RegExp ("pattern", ["flags"])
Var s = "number 123, letter abc, underline _! ";
Var re = new RegExp ("(\ w) \ w *", "g"); // because \ is also an escape character in quotation marks, you need to add one more \
Alert(re.exe c (s); // 123,1

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