Regular expression is the most important part in form validations and it is widely used for search, replace and web crawling systems. If you want to write a selector engine (used to find elements in a DOM), it should be possible with Regular Expressions. In this post we explained few tips that how to understand and write the Regular Expression in simple way.
Author
Arun Kumar Sekar
Engineer, Plugin Expert
Chennai, INDIA
Engineer, Plugin Expert
Chennai, INDIA
Will discuss about basic regular expression in three stages.
Stage 1
Symbol Explanation^ Start of string
$ End of string
. Any single character
+ One or more character
\ Escape Special characters
? Zero or more characters
Input exactly match with “abc”
var A = /^abc$/;
Input start with “abc”
var B = /^abc/;
Input end with “abc”
var C = /abc$/;
Input “abc” and one character allowed Eg. abcx
var D = /^abc.$/;
Input “abc” and more than one character allowed Eg. abcxy
var E = /^abc.+$/;
Input exactly match with “abc.def”, cause (.) escaped
var F = /^abc\.def$/;
Passes any characters followed or not by “abc” Eg. abcxyz12....
var G = /^abc.+?$/
Stage 2
Char Group Explanation
[abc] Should match any single of character
[^abc] Should not match any single character
[a-zA-Z0-9] Characters range lowercase a-z, uppercase A-Z and numbers
[a-z-._] Match against character range lowercase a-z and ._- special chats
(.*?) Capture everything enclosed with brackets
(com|info) Input should be “com” or “info”
{2} Exactly two characters
{2,3} Minimum 2 characters and Maximum 3 characters
{2,} More than 2 characters
Put together all in one URL validation.
var URL = /^(http|https|ftp):\/\/(www+\.)?[a-zA-Z0-9]+\.([a-zA-Z]{2,4})\/?/;
URL.test(“https://9lessons.info”); // pass
URL.test(“https://www.9lessons.info”); // pass
URL.test(“https://9lessons.info/”); // pass
URL.test(“https://9lessons.info/index.html”); // pass
URL.test(“https://9lessons.info”); // pass
URL.test(“https://www.9lessons.info”); // pass
URL.test(“https://9lessons.info/”); // pass
URL.test(“https://9lessons.info/index.html”); // pass
Stage 3
Short Form Equivalent Explanation
\d [0-9] Any numbers
\D [^0-9] Any non-digits
\w [a-zA-Z0-9_] Characters,numbers and underscore
\W [^a-zA-Z0-9_] Except any characters, numbers and underscore
\s - White space character
\S - Non white space character
var number = /^(\+\d{2,4})?\s?(\d{10})$/; // validating phone number
number.test(1111111111); //pass
number.test(+111111111111); //pass
number.test(+11 1111111111); //pass
number.test(11111111); //Fail
number.test(1111111111); //pass
number.test(+111111111111); //pass
number.test(+11 1111111111); //pass
number.test(11111111); //Fail
Very nice post , Cool and simple
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This is a great tutorial :) Can you write a tutorial for .htaccess like this ? it will be very help full. Thank you ! :)
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pass too. So something is wrong.
It's very useful. thanks
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ReplyDeleteGood Job. However my Suggestions are below.Correct me if i am wrong
Possible Errors are: multiple wwwwww will be accepted.
It should Be www? not www+
And
([a-zA-Z]{2,4})\/?/ it should be ([a-zA-Z]{2,4})(\/|\?|$) to restrict the .com,in,.edun,etc then / or ? then any thing else can come
So that below url ll be restricted
URL.test("http://www.9lessons.inoofscriptalert(1)/scriptoo");
The Final Regex is:
"/^(http|https|ftp):\/\/(www?\.)?[a-zA-Z0-9]+\.([a-zA-Z]{2,4})(\/|\?|$)/"
great tutorial,,,tanks bro
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Please Update:
ReplyDelete/^(http|https|ftp):\/\/(www?\.)?[a-zA-Z0-9]+\.([a-zA-Z]{2,4})(\/|\?|$)/
Great............
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