Regular Expression are very important in professional JavaScript.
There is a wonderful
resource in Mozilla developer center.
Two ways to construct a regular expression
1. Literal expression
re = /ab+c/g;
2. Constructor function
re = new RegExp("ab+c", "g");
Possible Flags
1. g - global search.
2. i - case-insensitive search.
3. m - multi-line search.
Simple and Special characters
A regular expression is composed of simple characters (such as /abc123_/) and special
characters.
Some important special characters:
1. ^ - Matches beginning of input.
2. $ - Matches end of input.
3. * - Matches the preceding character 0 or more times.
4. + - Matches the preceding character 1 or more times.
5. ? - Matches the preceding character 0 or 1 time.
6. . - Matches any single character.
Sepcial character \
There are two meanings of the special charater.
1. Used before simple character, indicating that the next character is special.
e.g. b is a simple character, \b is used to indicate a word
boundary.
Some important special character with \:
1. \b - Matches a word boundary.
2. \d - Matches a digit character.
3. \s - Matches a white space character, including space,
tab, line feed.
4. \w - Matches any alphanumeric character including the
underscore. Equivalent to [A-Za-z0-9_].
JavaScript funtions to operate regular expression
1. exec - returns: array.
2. match - returns: array or null.
3. test - returns: true or false.
4. search - returns: index or -1.
5. replace - returns: string.
Examples:
/d(b+)d/g.exec("cdbbdbsbz"); // ["dbbd", "bb"]
"cdbbdbsbz".match(/d(b+)d/g); // ["dbbd"]
"cdbbdbsbz".search(/d(b+)d/g); // 1
/d(b+)d/g.test("cdbbdbsbz"); // true