Explain with example the RegExp Object in javascript

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Amrith Chandran · Answer

Regular expression (RegExp) is a sequence of characters that forms a search pattern. It is used for pattern matching and string manipulation in JavaScript.
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Creating a RegExp Object
There are two ways to create a regular expression are given as below,
Using Literal Notation
let pattern = /hello/;
Using the RegExp Constructor
let pattern = new RegExp("hello");
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Difference:and 
Constructors allow dynamic pattern creation, while literal notation is simpler and more commonly used.
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RegExp Methods
there are several RegExp methods to match a pattern in a given variable values,
test() - Checks if a pattern exists
Returns true or false depending on whether the pattern is found or not.
let regex = /hello/;
console.log(regex.test("hello world"));  // true
console.log(regex.test("hi there"));     // false
match() - Finds matches in a string
Returns an array of matches, or return null if no matches are found.
let str = "hello world, hello JS";
console.log(str.match(/hello/g));  // ["hello", "hello"]
replace() - Replaces matched text
It replaces a specific pattern match in given values
let text = "hello world";
console.log(text.replace(/hello/, "Hi"));  
//Output: "Hi world"
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search() - Returns the index of the first match
It matches a pattern in a given value or we can say that it search a specific pattern in the given value and returns the index number if found.
let sentence = "JavaScript is awesome!";
console.log(sentence.search(/is/));  
//Output: 11 (index)
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split() - Splits a string using a regex pattern
let data = "apple,banana,orange";
console.log(data.split(/,/));  // ["apple", "banana", "orange"]
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RegExp Flags (Modifiers)
Flags modify the way the regular expression works.
g : Global match (find all matches)i : and Case-insensitive matchm : Multi-line match
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Example:
let caseInsensitive = /hello/i;
console.log(caseInsensitive.test("HELLO"));  // true
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RegExp Special Characters and Metacharacters
\d: Matches a digit (0-9)
\D: Matches a non-digit
\w: Matches an alphanumeric character (A-Z, a-z, 0-9, _)
\W: Matches a non-word character
\s: Matches whitespace
\S: Matches non-whitespace
^: Matches the start of a string
$: Matches the end of a string
.*: Matches any character(s)
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Example:
let numRegex = /\d+/;
console.log("Order #1234".match(numRegex));  // ["1234"]
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I hope you understand clearly the RegExp object in javascrip.
Thanks.
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Also, read: 
Explain the Date object in javascript. and 
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Explain with example the RegExp Object in javascript

Ashutosh Kumar Verma

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1 Answers

RegExp Methods

RegExp Flags (Modifiers)

RegExp Special Characters & Metacharacters

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