JavaScript Regular Expressions Part1 - JavaScript Tutorial 88

Опубликовано: 28 Сентябрь 2024
на канале: ChidresTechTutorials

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Notes for You:: JavaScript Regular Expressions Part1 - JavaScript Tutorial 88

What is RegExp:
- RegExp is a built-in object, used to define a search pattern (or regular expression), which can be used to make a wide variety of tests on a given string.

Application of Regular Expressions:
- Search for a word(s) in a given string
- Find & replace a word(s) in a given string
- Perform data validations etc. etc.

1. Defining regular expression using RegExp object constructor notation:

Syntax:
var variableName = new RegExp("search pattern", ["flags"] ) ;

Ex: phone number validation
var pattern = new RegExp("^[0-9]{10}$") ;

2. Defining regular expression using RegExp literal notation:

Syntax:
var variableName = /search pattern/ [flags] ;

Ex: phone number validation
var pattern = /^[0-9]{10}$/;

JavaScript RegExp Methods:

test() Method:
- is used to test is there match or no match between regular expression and the given string.
- If there is a match then it returns true otherwise returns false.

Syntax
pattern.test(str:String):Boolean

Ex:
var phoneNumber = "1234567891";
var pattern = /^[0-9]{10}$/;
document.write(pattern.test(phoneNumber)); // true

exec() Method:
- is used to search for an occurrence(s) of a pattern in a given string.
- Returns an array with found pattern, it's index and some other extra properties otherwise returns null.

Note: exec method updates itself for the next match.

Syntax
pattern.exec(str:String):array

Example code:
var myName = "I am Javascript. I am the best. I am lovely";
var pattern = /am/g;
var rArray=[];

while( (rArray = pattern.exec(myName)) != null)
{
document.write("found word : ",rArray[0],"<br/>");
document.write("location: ",rArray.index,"<br/>");
}

Note:
- replace < with less-than symbol.
- replace > with greater-than symbol.

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JavaScript Tutorial 89 - Regular Expression Flags in JavaScript
   • JavaScript Regular Expressions Part2 ...

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JavaScript Tutorial 87 - String Methods in JavaScript | JavaScript String Methods
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