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Regex remove all string start with special character

I have a string look like:
var str = https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none
I want to remove at start ?pid= to end. The result look like:
var str = https://sharengay.com/movie13.m3u8
I tried to:
str = str.replace(/^(?:?pid=)+/g, "");
But it show error like:
Invalid regular expression: /^(?:?pid=)+/: Nothing to repeat

If you really want to do this at the string level with regex, it's simply replacing /\?pid=.*$/ with "":
str = str.replace(/\?pid=.*$/, "");
That matches ?pid= and everything that follows it (.*) through the end of the string ($).
Live Example:
var str = "https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none";
str = str.replace(/\?pid=.*$/, "");
console.log(str);

You can use split
var str = "https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none"
var result = str.split("?pid=")[0];
console.log(result);

You can simply use split(), which i think is simple and easy.
var str = "https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none";
str = str.split("?pid");
console.log(str[0]);

You may create a URL object and concatenate the origin and the pathname:
var str = "https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none";
var url = new URL(str);
console.log(url.origin + url.pathname);

You have to escape the ? and if you want to remove everything from that point you also need a .+:
str = str.replace(/\?pid=.+$/, "")

You can use split function to get only url without query string.
Here is the example.
var str = 'https://sharengay.com/movie13.m3u8?pid=144.21.112.0&tcp=none';
var data = str.split("?");
alert(data[0]);

Find last string after delimiter: Javascript

I have a url with many delimiters '/'.
I want to find the string after the last delimiter. How can I write a javascript code?
for eg if my url is
localhost/sample/message/invitation/create/email
I want to display 'email' as my output.

var last = input.split("/").pop();
Simples!

Splitting on a regex that matches spaces or hyphens and taking the last element
var lw = function(v) {
return (""+v).replace(/[\s-]+$/,'').split(/[\s-]/).pop();
};
lw('This is a test.'); // returns 'test.'
lw('localhost/sample/message/invitation/create/email,'); // returns 'email,'

var url="localhost/sample/message/invitation/create/email";
url.split("/").pop()
or
var last=$(url.split("/")).last();

Usng simple regex
var str = "localhost/sample/message/invitation/create/email";
var last = str.match(/[^/]*$/)[0]";
Above regex return all character after last "/"

how to get numbers from a string in javascript?

I have
"id": 1468306
inside of a string, how can I use regular expression to get the number 1468306 for it?

You can use this regex:
/: (\d+)/
as in:
s = '"id": 1468306';
r = /: (\d+)/;
console.log(r.exec(s)[1]);
Output:
1468306

you can use parseInt() method in javascript as follows:
var str = parseInt(id);

Following code may help you:
var input = '"id": 1468306';
var matches = input.match(/"id": (\d+)/);
var id = matches[1];
The id get the required number.

JSON.parse("{" + yourString + "}").id
Will be your number if you have that in a String.

Fiddle: http://jsfiddle.net/SfeMh/
var regEx = /\d+/g;
var str = '"id": 1468306';
var numbers = str.match(regEx);
alert(numbers); // returns 1468306
It looks like you're trying to parse a JSON String. Try this way as already mentioned:
var parsedObj = JSON.parse(myJSONString);
alert(parsedObj.id); // returns 1468306

This will match in this cases
id : 156454;
id :156454;
id:156454;
/id\s?[:]\s?[0-9]+/g.match(stringhere)

Alright, my JSON answer still stands, use it if that's your full string you're giving us in the question. But if you really want a regex, here's one that will search for "id" and then find the number after.
parseInt(yourString.match(/("id"\s?:\s?)(\d+)/)[2])
Fiddle: http://jsfiddle.net/tS9M4/

Add line breaks after n numbers of letters in long words

A have a string that can reach up to 100 characters in lenght. Is there an easy way to insert line breaks in the word every 10th letter? For example:
aaaaaaaaaaaaaaaaaaaaaaaaa
Should turn in to
aaaaaaaaaa<br/>aaaaaaaaaa<br/>aaaaa
I know that i can modify html with the html() method, but im not sure how to count characters and insert the tags. Thanks

Here is one option:
string.match(/.{1,10}/g).join("<br/>");

Assuming the text is inside a div or a span:
<div id="myDiv">aaaaaaaaaaaaaaaaaaaaaaaaa</div>
You can do:
$(function() {
var html=$('#myDiv').html();
var newHtml='';
for (var i=0;i<html.length;i++) {
newHtml=newHtml+html[i];
if ((i+1)%10==0) {newHtml=newHtml+'<br/>';}
}
$('#myDiv').html(newHtml);
});
Here is example: http://jsfiddle.net/68PvB/
Good Luck!

If you have your string in a variable you can use its replace method like this:
var chunklen = 2; //the length of the chunks you require
var str = '123456789'; //your string
var rxp = new RegExp( '(.{'+chunklen+'})', 'g' );
var str2 = str.replace( rxp, '$1<br/>' );
console.log( str2 ); //12<br/>34<br/>56<br/>78<br/>9

find special text from string in javascript

I have string like #ls/?folder_path=home/videos/
how i can find last text from string? this place is videos
other strings like
#ls/?folder_path=home/videos/
#ls/?folder_path=home/videos/test/testt/
#ls/?folder_path=seff/test/home/videos/

We could use a few more example strings, but based off of your one and only example, here's a rough regex to get you started:
.*?/\?.*?/(.*?)\//
EDIT:
Based on your extended examples:
.*?/\?.*/(.*?)\//
This regex will consume text until the second to last / and capture until the last / in the string.

This will work even if the string doesn't end in /
var str;
var re = /\w+(?=\/?$)/;
str = "#ls/?folder_path=home/videos/"
str.match(re) ; //# => videos
str = "#ls/?folder_path=home/videos/test/testt/"
str.match(re) ; //# => testt
str = "#ls/?folder_path=seff/test/home/videos/"
str.match(re) ; //# => videos
str = "#ls/?folder_path=home/videos/test/testt"
str.match(re) ; //# => testt

\/([^\/]*)\/?$
This regex will match all non / between the last two /. Where the last / is optional. The $ is matching the end of the string.
Your resulting string is then in the first capturing group (because of the ()) $1
You can test it here

There are many ways to do this. One of them:
var str = '#ls/?folder_path=home/videos/'.replace(/\/$/,'');
alert(str.substr(str.lastIndexOf('/')+1)); //=> videos
Alternative without using replace
var str = '#ls/?folder_path=home/videos/'
,str = str.substr(0,str.length-1)
,str = str.substr(str.lastIndexOf('/')+1);
alert(str); //=> videos

If your data is consistent like this string, this is a simple split based way to retreive
your required string: http://jsfiddle.net/EEkLP/
var str="#ls/?folder_path=home/videos/";
var strArr = str.split("/");
alert(strArr[strArr.length-2]);

If it always ends with / then this will works.
var str = '#ls/?folder_path=home/videos/';
var arr = str.split('/');
var index = arr.length-2;
console.log(arr[index]);

If the last word always enclosed with forward slashes, then you can try this -
".+\/([^\/]+)\/$"
or in regex notation
/.+\/([^\/]+)\/$/