Today I am going to write a tutorial on Regular Expression which is needed in daily basis of our programming life. And some of friends will agree with me that it can make us a little bit of trouble. But nothing to worry my dear friends . Here is the shortcut which i used in my programming life. If you don't like it please don't mind on me because i am not a good blogger !!
RegExp has exec and test method
string has match,replace,search,split method for regular expression
var re = /ab+c/; // You can call this way to initialize regular expression pattern
var re = new RegExp("ab+c"); // more standard when you not know the pattern [This is construct way]
/a*/ matches aaaaaaaa o or more times
but /a\*/ matches only a*
/a\b/ matches a with boundary word.
^ matches beginning of input like as /^a/ matches in "a teddy bear" but not "A in E"
/ (foo) (bar) \1 \2/ // matches and remember first two words these called capturing parenthesis
/ (?:foo){1,2}/ non capturing parenthesis but not foo in "foo foo" but o in "foo"
x(?=y) match only if x is followed by y this is called look ahead
/ Jack (?=Frost|Sprat) / matches only jack followed by Frost or Jack Sprat.
x(?!y) match only if x is not followed by y negated look ahead
example : /\d+(?!\.)/ that matches "141" but not "3.141"
x|y matches either x or y
example : /green|red/ matches either in "green apple" or "red apple"
{n} matches exactly n occurrence of the preceding character
example : /a{2}/ matches in "caandy" but not in "candy"
{n,m} matches at least n and at most m occurrence of the preceding character
example : /a{1,2}/ matches 1 for in "Candy" , 2 for in "Caandy" , 3 for "Caaandy" and also in "Caaaaaaaaandy" because its matches preceding 3a like aaa
[xyz] matches any of the characters in brackets , this is same as [x-z]
example : [abcd] matches the 'b' in "brisket" and the 'c' in "city". The patterns /[a-z.]+/ and /[\w.]+/ match the entire string "test.i.ng".
[^xyz] it matches anything that is not enclosed in the brackets
example: [^a-c] matches r in "briefcase"
[\b] matches a backspaces
\b matches a word boundary example: /\bm/ matches the m in "moon" , but /\boo/ does not matches oo in "moon" because oo is followed by n , /oon\b/ matches in "moon" because oon is the end of word boundary.
\d matches a digit character equivalent to [0-9]
\s matches a single white space character example: /\s\w*/ matches bar in "foo bar".
\w matches a alpha numeric character including the underscore equivalent to [A-Za-z0-9_]
Example with JavaScript (how to implement)
RegExp has exec and test method
string has match,replace,search,split method for regular expression
var re = /ab+c/; // You can call this way to initialize regular expression pattern
var re = new RegExp("ab+c"); // more standard when you not know the pattern [This is construct way]
/a*/ matches aaaaaaaa o or more times
but /a\*/ matches only a*
/a\b/ matches a with boundary word.
^ matches beginning of input like as /^a/ matches in "a teddy bear" but not "A in E"
/ (foo) (bar) \1 \2/ // matches and remember first two words these called capturing parenthesis
/ (?:foo){1,2}/ non capturing parenthesis but not foo in "foo foo" but o in "foo"
x(?=y) match only if x is followed by y this is called look ahead
/ Jack (?=Frost|Sprat) / matches only jack followed by Frost or Jack Sprat.
x(?!y) match only if x is not followed by y negated look ahead
example : /\d+(?!\.)/ that matches "141" but not "3.141"
x|y matches either x or y
example : /green|red/ matches either in "green apple" or "red apple"
{n} matches exactly n occurrence of the preceding character
example : /a{2}/ matches in "caandy" but not in "candy"
{n,m} matches at least n and at most m occurrence of the preceding character
example : /a{1,2}/ matches 1 for in "Candy" , 2 for in "Caandy" , 3 for "Caaandy" and also in "Caaaaaaaaandy" because its matches preceding 3a like aaa
[xyz] matches any of the characters in brackets , this is same as [x-z]
example : [abcd] matches the 'b' in "brisket" and the 'c' in "city". The patterns /[a-z.]+/ and /[\w.]+/ match the entire string "test.i.ng".
[^xyz] it matches anything that is not enclosed in the brackets
example: [^a-c] matches r in "briefcase"
[\b] matches a backspaces
\b matches a word boundary example: /\bm/ matches the m in "moon" , but /\boo/ does not matches oo in "moon" because oo is followed by n , /oon\b/ matches in "moon" because oon is the end of word boundary.
\d matches a digit character equivalent to [0-9]
\s matches a single white space character example: /\s\w*/ matches bar in "foo bar".
\w matches a alpha numeric character including the underscore equivalent to [A-Za-z0-9_]
Example with JavaScript (how to implement)
var myReg = /a(m+)i/g;
var myArray = myReg.exec("programming"); // Or this way If you want to construct the regular expression from a string var myReg = new RegExp("a(m+)iprogramming
