JavaScript Regular Expressions Part2 - JavaScript Tutorial 89

Published: 22 January 2022
on channel: ChidresTechTutorials

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Notes for You:: JavaScript Regular Expressions Part2 - JavaScript Tutorial 89
JavaScript RegExp Object - using flags:
Sequence of characters enclosed in between pair of forward slash symbols indicates a regular expression in JavaScript.

Syntax for defining a variable of type regular expression is:
var variableName = /search pattern/ [flags] ;

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

Flags:
indicate how a regular expression must be interpreted.

Ex:
i: ignore case
indicates ignore the difference between lower case characters and upper case characters.

g: global match
indicates find all occurrences of the pattern rather than stopping at the first occurrence.

Code to understand i flag:

/*
var str = "Agent007";
var pattern = /Agent/;
var rArray = [];

rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], " "); // Agent
d.w("location: ", rArray.index, " "); // 0
*/

/*
var str = "Agent007";
var pattern = /agent/;
var rArray = [];

rArray = pattern.exec(str); // null
d.w("found word: ", rArray[0], " "); // error
d.w("location: ", rArray.index, " "); // error
*/

var str = "Agent007";
var pattern = /agent/i;
var rArray = [];

rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], " "); // Agent
d.w("location: ", rArray.index, " ");// 0

Code to understand g flag:

/*
var str = "Agent007 is the best agent";
var pattern = /agent/i;
var rArray = [];

rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], " "); // Agent
d.w("location: ", rArray.index, " "); // 0

rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], " "); // Agent
d.w("location: ", rArray.index, " "); // 0
*/

var str = "Agent007 is the best agent";
var pattern = /agent/ig;
var rArray = [];

/*
rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], " "); // Agent
d.w("location: ", rArray.index, " "); // 0

rArray = pattern.exec(str); // ["agent"]
d.w("found word: ", rArray[0], " "); // agent
d.w("location: ", rArray.index, " "); // 21

rArray = pattern.exec(str); // null
d.w("found word: ", rArray[0], " "); // error
d.w("location: ", rArray.index, " "); // error
*/

// OR

while( (rArray = pattern.exec(str)) != null ){
d.w("found word: ", rArray[0], " ");
d.w("location: ", rArray.index, " ");
}

Note:
replace d.w with document.write.
replace < with less-than symbol.
replace > with greater-than symbol.

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Follow the link for next video:
JavaScript Tutorial 90 - Regular Expression Meta Characters in JavaScript
 • JavaScript Regular Expressions Part3 ...

Follow the link for previous video:
JavaScript Tutorial 88 - JavaScript RegExp Object
 • JavaScript Regular Expressions Part1 ...

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