A brief discussion on JS regular RegExp object

1. RegExp object
2. Grammar

2.1 Definition
2.2 Modifiers
2.3 Square brackets
2.4 Metacharacters
2.5 Quantifiers
2.6 Methods

1. RegExp object

Regular expressions are objects that describe character patterns.
Regular expressions are used to match string patterns and perform search and replacement. They are a powerful tool for performing pattern matching on strings.
Reference: w3cschool | JavaScript RegExp Object

2. Grammar

2.1 Definition

When creating a regular expression object using the constructor, normal character escape rules are required (prefixed with a backslash \)

/* For example, the following two definitions are equivalent*/

// Constructor method const reg = new RegExp("\\w+");
// Literal method const reg = /\w+/;

2.2 Modifiers

Used to perform case-sensitive and global matching

Modifiers	describe
i	Performs a case-insensitive match.
g	Perform a global match (find all matches instead of stopping after the first one).
m	Performs a multi-line match.

    /* chestnut*/
const reg = /\w/gi

2.3 Square brackets

Used to find characters within a range:

expression	describe
[abc]	Finds any character between the square brackets.
[^abc]	Finds any character that is not between the square brackets.
[0-9]	Finds any number from 0 to 9.
[az]	Finds any character from lowercase a to lowercase z.
[AZ]	Finds any character from uppercase A to uppercase Z.
[Az]	Finds any character from uppercase A to lowercase z.
[adgk]	Finds any character in the given set.
[^adgk]	Finds any character outside the given set.
(red\|blue\|green)	Finds any of the specified options.

/* chestnut*/
const reg = /[0-9]/g

2.4 Metacharacters

are characters with special meanings:

Metacharacters	describe
.	Searches for a single character, except newline and line terminator.
\w	Find word characters.
\W	Find non-word characters.
\d	Find a number.
\D	Find non-numeric characters.
\s	Finds whitespace characters.
\S	Finds non-whitespace characters.
\b	Matches a word boundary.
\B	Matches a non-word boundary.
\0	Finds a NUL character.
\n	Finds a newline character.
\f	Finds a form feed character.
\r	Find the carriage return character.
\t	Find the tab character.
\v	Finds a vertical tab character.
\xxx	Searches for the character specified by the octal number xxx.
\xdd	Searches for the character specified by hexadecimal number dd.
\uxxxx	Finds the Unicode character specified by the hexadecimal number xxxx.

/* chestnut*/
const reg = /\d/g // matches numbers

2.5 Quantifiers

are characters with special meanings:

quantifier	describe
n+	Matches any string containing at least one n.
n*	Matches any string containing zero or more occurrences of n.
n?	Matches any string containing zero or one n.
n{X}	Matches a string containing a sequence of X n's.
n{X,Y}	Matches a string containing a sequence of X to Y n's.
n{X,}	Matches a string containing a sequence of at least X n's.
n$	Matches any string ending with n.
^n	Matches any string beginning with n.
?=n	Matches any string that is immediately followed by the specified string n.
?!n	Matches any string that is not immediately followed by the specified string n.

/* chestnut*/
const reg = /\d+/g // matches at least one digit

2.6 Methods

are characters with special meanings:

method	describe	FF	IE
compile	Compile a regular expression.	1	4
exec	Retrieves the value specified in a string. Returns the found value and identifies its position.	1	4
test	Retrieves the value specified in a string. Returns true or false.	1	4

method	describe	FF	IE
search	Retrieves values that match a regular expression.	1	4
match	Finds one or more matches of the regular expression.	1	4
replace	Replaces substrings that match a regular expression.	1	4
split	Split a string into an array of strings.	1	4

/* chestnut*/
var patt = /Hello/g
var result = patt.test(str) // Search for the string Hello -> true

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