RegExp stands for Regular Expression. A regular expression is a sequence of characters that forms a search pattern. The search pattern can be used for text search and text to replace operations. A regular expression can be a single character or a more complicated pattern.
Syntax:
new RegExp("(Regular Expressioncharactersnonword)")
Example: This example searches the words whose starting character is “A” and ending character is “C” with only one character in between them.
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<title>
JavaScript RegExp Reference
</title>
</head>
<body style="text-align:center">
<h1 style="color:green">
GeeksforGeeks
</h1>
<h2>RegExp . Metacharacter</h2>
<p>
Input String: ABC, A3C, A C, AXXCC!
</p>
<button onclick="geek()">
Click it!
</button>
<p id="app"></p>
<script>
function geek() {
let str1 = "ABC, A3C, A C, AXXCC!";
let regex4 = /A.C/g;
let match4 = str1.match(regex4);
document.getElementById("app").innerHTML =
"Found " + match4.length
+ " matches: " + match4;
}
</script>
</body>
</html>
|
Output:
The complete list of JavaScript RegExp is listed below:
JavaScript RegExp Constructor: In JavaScript, a constructor gets called when an object is created using the new keyword.
| Constructor |
Description |
Example |
| RegExp() |
It creates a new RegExp object |
|
JavaScript RegExp Properties: A JavaScript property is a member of an object that associates a key with a value.
- Instance Property: An instance property is a property that has a new copy for every new instance of the class.
| Instance Properties |
Description |
Example |
| constructor |
Return the RegExp constructor function for the object. |
|
| dotAll |
It checks if the ‘s’ flag is used or not in the Regular Expression |
|
| flags |
This property returns the flag being used in the current RegExp object |
|
| global |
It specifies whether the ‘g’ flag is used or not |
|
| hasIndices |
It specifies whether the ‘d’ flag is used or not |
|
| ignoreCase |
It specifies whether the ‘i’ flag is used or not |
|
| multiline |
It specifies whether ‘m’ flag is set or not |
|
| source |
It returns the text of the RegExp object |
|
| sticky |
It specifies whether ‘y’ flag is used or not |
|
| unicode |
It specifies whether ‘u’ flag is used or not |
|
| lastIndex |
It specifies at which index to start the next match |
|
JavaScript RegExp Methods: JavaScript methods are the actions that can be performed on objects.
- Instance Method: If the method is called on an instance of a RegExp then it is called an instance method.
| Instance Methods |
Description |
Example |
| exec |
It is used to test if the strings match |
|
| test |
It also checks if the string matches but the return type is different |
|
| toString |
It returns the string value of the Regular Expression |
|
The different Metacharacters and Flags of RegExp is given below:
|
RegExp
|
Description
|
Example
|
| Metacharacter |
Search single characters, except line terminator or newline. |
|
| m |
Perform multiline matching. |
|
| \r |
The RegExp \r Metacharacter carriage return characters. |
|
| [abc] |
Search for any character which is between the brackets. |
|
| (x|y) |
Search any of the specified characters (separated by |). |
|
| \xxx |
Find the character specified by an octal number xxx. |
|
| \W |
Find the non word character i.e. characters which are not from a to z, A to Z, 0 to 9. |
|
| [^abc] |
Search for any character which is not between the brackets. |
|
| g |
Find all the occurrences of the pattern instead of stopping after the first match i.e it performs a global match. |
|
| [0-9] |
Search any digit which is between the brackets. |
|
| \s |
Find the whitespace characters. |
|
| \b |
Find a match at the beginning or end of a word |
|
| i |
Perform case-insensitive matching in the string. |
|
| \n |
The RegExp \n Metacharacter in JavaScript is used to find the newline character. |
|
| [^0-9] |
Search for any digit which is not between the brackets. |
|
| \B |
Find a match that is not present at the beginning or end of a word. |
|
| \f |
Find the form feed character (form feed is a page-breaking ASCII control character). |
|
| \w |
Find the word character i.e. characters from a to z, A to Z, 0 to 9. It is the same as [a-zA-Z_0-9]. |
|
| \d |
Search digit characters. It is the same as [0-9]. |
|
| \t |
If it is found it returns the position else it returns -1. |
|
| \D |
Search non-digit characters i.e all the characters except digits. It is the same as [^0-9]. |
|
| \0 |
Find the NULL character. If it is found it returns the position else it returns -1. |
|
| \v |
Find the vertical tab character. If it is found it returns the position else it returns -1. |
|
| * |
Find the match of any string that contains zero or more occurrences of m. |
|
| {X,} |
Find the match of any string that contains a sequence of m, at least X times, where X is a number. |
|
| ?! |
Find the match of any string which is not followed by a specific string m. |
|
| {X} |
Find the match of any string that contains a sequence of m, X times where X is a number. |
|
| ^ |
Find the match of any string which contains m at the beginning of it. |
|
| ? |
Find the match of any string that contains zero or one occurrence of m. |
|
| $ |
Find the match of any string which contains m at the end of it. |
|
| + |
Find the match of any string that contains at least one m. |
|
| \uxxxx |
Find the Unicode character specified by a hexadecimal number XXXX. |
|
| {X,Y} |
Find the match of any string that contains a sequence of m, X to Y times where X, Y must be numbered. |
|
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Last Updated :
30 May, 2023
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