JavaScript Regular Expressions Part2 - JavaScript Tutorial 89
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], "<br/>"); // Agent
d.w("location: ", rArray.index, "<br/>"); // 0
*/
/*
var str = "Agent007";
var pattern = /agent/;
var rArray = [];
rArray = pattern.exec(str); // null
d.w("found word: ", rArray[0], "<br/>"); // error
d.w("location: ", rArray.index, "<br/>"); // error
*/
var str = "Agent007";
var pattern = /agent/i;
var rArray = [];
rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], "<br/>"); // Agent
d.w("location: ", rArray.index, "<br/>");// 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], "<br/>"); // Agent
d.w("location: ", rArray.index, "<br/>"); // 0
rArray = pattern.exec(str); // ["Agent"]
d.w("found word: ", rArray[0], "<br/>"); // Agent
d.w("location: ", rArray.index, "<br/>"); // 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], "<br/>"); // Agent
d.w("location: ", rArray.index, "<br/>"); // 0
rArray = pattern.exec(str); // ["agent"]
d.w("found word: ", rArray[0], "<br/>"); // agent
d.w("location: ", rArray.index, "<br/>"); // 21
rArray = pattern.exec(str); // null
d.w("found word: ", rArray[0], "<br/>"); // error
d.w("location: ", rArray.index, "<br/>"); // error
*/
// OR
while( (rArray = pattern.exec(str)) != null ){
d.w("found word: ", rArray[0], "<br/>");
d.w("location: ", rArray.index, "<br/>");
}
Note:
replace d.w with document.write.
replace < with less-than symbol.
replace > with greater-than symbol.
=========================================
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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