Develop Reference

Javascript Dynamic Regex Generation

I want to make my alphanumeric regex dynamic in a way that it takes the allowed special characters with it as an argument by the user. Following is my code ... I am getting quotes error here .... any body can tell me how to go about it ?
function aplhanumeric(value,allowed){
///^[a-z0-9_\-]+$/i
alert(allowed);
if(allowed != ''){
var regex = new RegExp('/^[a-z0-9_\' + allowed + ']+$/i');
return (value.match(regex));
}else{
return (alphaNumericRegex.test(value));
}
}

You've actually escaped the quote, so you have to escape the escape
var regex = new RegExp("^[a-z0-9_\\" + allowed + "]+$", "i");

How to remove the first and the last character of a string

I'm wondering how to remove the first and last character of a string in Javascript.
My url is showing /installers/ and I just want installers.
Sometimes it will be /installers/services/ and I just need installers/services.
So I can't just simply strip the slashes /.

Here you go
var yourString = "/installers/";
var result = yourString.substring(1, yourString.length-1);
console.log(result);
Or you can use .slice as suggested by Ankit Gupta
var yourString = "/installers/services/";
var result = yourString.slice(1,-1);
console.log(result);
Documentation for the slice and substring.

It may be nicer one to use slice like :
string.slice(1, -1)

I don't think jQuery has anything to do with this. Anyway, try the following :
url = url.replace(/^\/|\/$/g, '');

If you dont always have a starting or trailing slash, you could regex it. While regexes are slower then simple replaces/slices, it has a bit more room for logic:
"/installers/services/".replace(/^\/?|\/?$/g, "")
# /installers/services/ -> installers/services
# /installers/services -> installers/services
# installers/services/ -> installers/services
The regex explained:
['start with' ^] + [Optional?] + [slash]: ^/?, escaped -> ^\/?
The pipe ( | ) can be read as or
['ends with' $] + [Optional ?] + [slash] -> /?$, escaped -> \/?$
Combined it would be ^/?|/$ without escaping. Optional first slash OR optional last slash.
Technically it isn't "optional", but "zero or one times".

You can do something like that :
"/installers/services/".replace(/^\/+/g,'').replace(/\/+$/g,'')
This regex is a common way to have the same behaviour of the trim function used in many languages.
A possible implementation of trim function is :
function trim(string, char){
if(!char) char = ' '; //space by default
char = char.replace(/([()[{*+.$^\\|?])/g, '\\$1'); //escape char parameter if needed for regex syntax.
var regex_1 = new RegExp("^" + char + "+", "g");
var regex_2 = new RegExp(char + "+$", "g");
return string.replace(regex_1, '').replace(regex_2, '');
}
Which will delete all / at the beginning and the end of the string. It handles cases like ///installers/services///
You can also simply do :
"/installers/".substring(1, string.length-1);

You can use substring method
s = s.substring(0, s.length - 1) //removes last character
another alternative is slice method

if you need to remove the first leter of string
string.slice(1, 0)
and for remove last letter
string.slice(0, -1)

use .replace(/.*\/(\S+)\//img,"$1")
"/installers/services/".replace(/.*\/(\S+)\//img,"$1"); //--> services
"/services/".replace(/.*\/(\S+)\//img,"$1"); //--> services

It is too nicer shortcode.
response.data.slice(1,-1) // "Prince"
-> Prince

url=url.substring(1,url.Length-1);
This way you can use the directories if it is like .../.../.../... etc.

Regex for empty string or white space

I am trying to detect if a user enter whitespace in a textbox:
var regex = "^\s+$" ;
if($("#siren").val().match(regex)) {
echo($("#siren").val());
error+=1;
$("#siren").addClass("error");
$(".div-error").append("- Champ Siren/Siret ne doit pas etre vide<br/>");
}
if($("#siren").val().match(regex)) is supposed to match whitespace string, however, it doesn' t seems to work, what am I doing wrong ?
Thanks for your helps

The \ (backslash) in the .match call is not properly escaped. It would be easier to use a regex literal though. Either will work:
var regex = "^\\s+$";
var regex = /^\s+$/;
Also note that + will require at least one space. You may want to use *.

If you are looking for empty string in addition to whitespace you meed to use * rather than +
var regex = /^\s*$/ ;
^

If you're using jQuery, you have .trim().
if ($("#siren").val().trim() == "") {
// it's empty
}

If one only cares about whitespace at the beginning and end of the string (but not in the middle), then another option is to use String.trim():
" your string contents ".trim();
// => "your string contents"

http://jsfiddle.net/DqGB8/1/
This is my solution
var error=0;
var test = [" ", " "];
if(test[0].match(/^\s*$/g)) {
$("#output").html("MATCH!");
error+=1;
} else {
$("#output").html("no_match");
}

Had similar problem, was looking for white spaces in a string, solution:
To search for 1 space:
var regex = /^.+\s.+$/ ;
example: "user last_name"
To search for multiple spaces:
var regex = /^.+\s.+$/g ;
example: "user last name"

How to ignore newline in regexp?

How to ignore newline in regexp in Javascript ?
for example:
data = "\
<test>11\n
1</test>\n\
#EXTM3U\n\
"
var reg = new RegExp( "\<" + "test" + "\>(.*?)\<\/" + "test" + "\>" )
var match = data.match(reg)
console.log(match[1])
result: undefined

In JavaScript, there is no flag to tell to RegExp() that . should match newlines. So, you need to use a workaround e.g. [\s\S].
Your RegExp would then look like this:
var reg = new RegExp( "\<" + "test" + "\>([\s\S]*?)\<\/" + "test" + "\>" );

You are missing a JS newline character \ at the end of line 2.
Also, change regexp to:
var data = "\
<test>11\n\
1</test>\n\
#EXTM3U\n\
";
var reg = new RegExp(/<test>(.|\s)*<\/test>/);
var match = data.match(reg);
console.log(match[0]);
http://jsfiddle.net/samliew/DPc2E/

By reading this one: How to use JavaScript regex over multiple lines?
I came with that, which works:
var data = "<test>11\n1</test>\n#EXTM3U\n";
reg = /<test>([\s\S]*?)<\/test>/;
var match = data.match(reg);
console.log(match[1]);
Here is a fiddle: http://jsfiddle.net/Rpkj2/

Better you can use [\s\S] instead of . for multiline matching.
It is the most common JavaScript idiom for matching everything including newlines. It's easier on the eyes and much more efficient than an alternation-based approach like (.|\n).

EDIT: Got it:
I tried to use this regex in notepad++ But the problem is that it finds the whole text from beginning to end
MyRegex:
<hostname-validation>(.|\s)*<\/pathname-validation> (finds everything)
/<hostname-validation>(.|\s)*<\/pathname-validation>/ (finds nothing)
/\<hostname-validation\>([\s\S]*?)\<\/pathname-validation\>/ (finds nothing)
**<hostname-validation>([\s\S]*?)<\/pathname-validation> (my desired result)**
The text where I use in:
<hostname-validation>www.your-tag-name.com</hostname-validation>
<pathname-validation>pathname</pathname-validation> <response-validation nil="true"/>
<validate-absence type="boolean">false</validate-absence> (...) <hostname-validation>www.your-tag-name.com</hostname-validation>
<pathname-validation>pathname</pathname-validation> <response-validation nil="false"/>
<validate-absence type="boolean">false</validate-absence> (...) <hostname-validation>www.your-tag-name.com</hostname-validation>
<pathname-validation>pathname</pathname-validation> <response-validation nil="true"/>
<validate-absence type="boolean">false</validate-absence> (...)

How can I find a specific string and replace based on character?

I'm trying to find a specific character, for example '?' and then remove all text behind the char until I hit a whitespace.
So that:
var string = '?What is going on here?';
Then the new string would be: 'is going on here';
I have been using this:
var mod_content = content.substring(content.indexOf(' ') + 1);
But this is not valid anymore, since the specific string also can be in the middle of a string also.
I haven't really tried anything but this. I have no idea at all how to do it.

use:
string = string.replace(/\?\S*\s+/g, '');
Update:
If want to remove the last ? too, then use
string = string.replace(/\?\S*\s*/g, '');

var firstBit = str.split("?");
var bityouWant = firstBit.substring(firstBit.indexOf(' ') + 1);