A brief introduction to the use of regular expressions in JavaScript_Basic knowledge

A regular expression is an object that describes a character pattern.

JavaScript's RegExp class represents regular expressions and string and regular expression definitions, using regular expressions to perform powerful pattern matching and search and replace text functionality.
Syntax:

Regular expressions can be defined using RegExp():

var pattern = new RegExp(pattern, attributes);

or simply

var pattern = /pattern/attributes;

Here is the description of the parameters:

• Pattern: A string specifying a regular expression or other regular expression pattern.
• attributes: Contains any "g", "i", and "m" attributes specified globally, each an optional string, case-insensitive and matching.

Brackets:

Brackets ([]) have special meaning when used in the context of regular expressions. They are used to find ranges of characters.

The range shown above is general; you can also use the range [0-3], which matches any decimal number from 0 through 3, or the range [b-v], which matches any lowercase letter, from b to v
Qualifier:

A frequency or sequence of characters within square brackets and the position of a single character can be represented by a special character. Each special character has a specific connotation. The , *, ?, and $ signs all follow a sequence of characters.
Example:

The following example will clear the concept about matching characters.

Literal characters:

Metacharacters are just preceded by a backslash, and their function is to combine alphabetic characters with special meanings.

For example, you can search for large monetary totals using the 'd' metacharacter: /([d] )000/, where d will search for any string of numeric characters.

The following is a list of metacharacters that can be used in Perl-style regular expressions.

Modifier

Several modifiers are available that can make working with regular expressions much easier, such as upper and lower case, searching across multiple lines, etc.