Javascript Regular Expression:Using Regex Subexpressions to extract part of string

The RegExp object provides an easy way to extract pieces of a string that

match parts of your patterns. This is accomplished by grouping

(placing parentheses around) the portions of the pattern

you wish to extract.

For example, suppose

you wished to extract first names and phone numbers from strings that

look like this,

FirstName MiddleName LastName NN-NNNNNNNNNN

For Pattern below

/([A-Z]{2,}) ([A-Z]{2,}) ([A-Z]{2,}) ([0-9]{2}-[0-9]{10})/

When it is applied to a string, the parentheses induce

subexpressions. When a match is successful, these parenthesized subexpressions

can be referred to individually by using static properties $1 to $9 of the

RegExp class object.

Code:

var customer = "SANGRAM SHIAVJI DESAI 91-9890868345";

//does not work as we need groups

//var pattern = /[A-Z]{2,} [A-Z]{2,} [0-9]{2}-[0-9]{10}/;

var pattern = /([A-Z]{2,}) ([A-Z]{2,}) ([A-Z]{2,}) ([0-9]{2}-[0-9]{10})/;

if(pattern.test(customer)){

console.log("Matching SubString:")

console.log("First Name:" + RegExp.$1);

console.log("MIDDLE NAME:"+ RegExp.$2)

console.log("LAST NAME:"+ RegExp.$3)

console.log("PHONE NO:"+ RegExp.$4)

}

Output:

Matching SubString:

First Name:SANGRAM

MIDDLE NAME:SHIAVJI

LAST NAME:DESAI

PHONE NO:91-9890868345

AS RegExp.$n is deprecated we need another way to access sub expression.

way one:

"exec" will execute the RegEx on the string. It will return an array.

To access $1 we access the 1 element of the array.

If it didn't match, it will return null instead of an array, if it returns null,

then the || will make it return blank array [] so we don't get errors.

The || is an OR so if the first side is a falsey value (the undefined of the exec)

it will return the other side.

Code:

var customer = "SANGRAM SHIAVJI DESAI 91-9890868345";

var pattern = /([A-Z]{2,}) ([A-Z]{2,}) ([A-Z]{2,}) ([0-9]{2}-[0-9]{10})/;

var resultText = pattern.exec(customer) || [] ;

console.log(resultText)

Output:

[

'SANGRAM SHIAVJI DESAI 91-9890868345',

'SANGRAM',

'SHIAVJI',

'DESAI',

'91-9890868345',

index: 0,

input: 'SANGRAM SHIAVJI DESAI 91-9890868345',

groups: undefined

]

way two:

Code:

var customer = "SANGRAM SHIAVJI DESAI 91-9890868345";

var pattern = /([A-Z]{2,}) ([A-Z]{2,}) ([A-Z]{2,}) ([0-9]{2}-[0-9]{10})/;

var firstName = customer.replace(pattern,'$1');

var middleName = customer.replace(pattern,'$2');

var lastName = customer.replace(pattern,'$3');

var cellNo = customer.replace(pattern,'$4');

Output:

console.log("First Name:",firstName)

console.log("Middle Name:" + middleName)

console.log("Last Name"+ lastName)

console.log("Cell No:" + cellNo)