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Removing elements of string before a specific repeated character in it in javascript

I'm trying to remove from my string all elements before an specific character which is repeated several times in this way:
let string = http://localhost:5000/contact-support
thus I´m just trying to remove everything before the third /
having as result:contact_support
for that i just set:
string.substring(string.indexOf('/') + 3);
Bust guess thats not the correct way
Any help about how to improve this in the simplest way please?
Thanks in advance!!!

It seems like you want to do some URL parsing here. JS brings the handful URL utility which can help you with this, and other similar tasks.
const myString = 'http://localhost:5000/contact-support';
const pathname = new URL(myString).pathname;
console.log(pathname); // outputs: /contact-support
// then you can also remove the first "/" character with `substring`
const whatIActuallyNeed = pathname.substring(1, pathname.length);
console.log(whatIActuallyNeed); // outputs: contact-support

Hope This will work
string.split("/")[3]
It will return the sub-string after the 3rd forward slash.

You could also use lastIndexOf('/'), like this:
string.substring(string.lastIndexOf('/') + 1);
Another possibility is regular expressions:
string.match(/[^\/]*\/\/[^\/]*\/(.*)/)[1];
Note that you must escape the slash, since it is the delimiter in regular expressions.

string.substring(string.lastIndexOf('/')+1) will also do the job if you are looking to use indexOf function explicitly.

Get base url from string with Regex and Javascript

I'm trying to get the base url from a string (So no window.location).
It needs to remove the trailing slash
It needs to be regex (No New URL)
It need to work with query parameters and anchor links
In other words all the following should return https://apple.com or https://www.apple.com for the last one.
https://apple.com?query=true&slash=false
https://apple.com#anchor=true&slash=false
http://www.apple.com/#anchor=true&slash=true&whatever=foo
These are just examples, urls can have different subdomains like https://shop.apple.co.uk/?query=foo should return https://shop.apple.co.uk - It could be any url like: https://foo.bar
The closer I got is with:
const baseUrl = url.replace(/^((\w+:)?\/\/[^\/]+\/?).*$/,'$1').replace(/\/$/, ""); // Base Path & Trailing slash
But this doesn't work with anchor links and queries which start right after the url without the / before
Any idea how I can get it to work on all cases?

You could add # and ? to your negated character class. You don't need .* because that will match until the end of the string.
For your example data, you could match:
^https?:\/\/[^#?\/]+
Regex demo
strings = [
"https://apple.com?query=true&slash=false",
"https://apple.com#anchor=true&slash=false",
"http://www.apple.com/#anchor=true&slash=true&whatever=foo",
"https://foo.bar/?q=true"
];
strings.forEach(s => {
console.log(s.match(/^https?:\/\/[^#?\/]+/)[0]);
})

You could use Web API's built-in URL for this. URL will also provide you with other parsed properties that are easy to get to, like the query string params, the protocol, etc.
Regex is a painful way to do something that the browser makes otherwise very simple.
I know that you asked about using regex, but in the event that you (or someone coming here in the future) really just cares about getting the information out and isn't committed to using regex, maybe this answer will help.
let one = "https://apple.com?query=true&slash=false"
let two = "https://apple.com#anchor=true&slash=false"
let three = "http://www.apple.com/#anchor=true&slash=true&whatever=foo"
let urlOne = new URL(one)
console.log(urlOne.origin)
let urlTwo = new URL(two)
console.log(urlTwo.origin)
let urlThree = new URL(three)
console.log(urlThree.origin)

const baseUrl = url.replace(/(.*:\/\/.*)[\?\/#].*/, '$1');

This will get you everything up to the .com part. You will have to append .com once you pull out the first part of the url.
^http.*?(?=\.com)
Or maybe you could do:
myUrl.Replace(/(#|\?|\/#).*$/, "")
To remove everything after the host name.

How would I write a Regular Expression to capture the value between Last Slash and Query String?

Problem:
Extract image file name from CDN address similar to the following:
https://cdnstorage.api.com/v0/b/my-app.com/o/photo%2FB%_2.jpeg?alt=media&token=4e32-a1a2-c48e6c91a2ba
Two-stage Solution:
I am using two regular expressions to retrieve the file name:
var postLastSlashRegEx = /[^\/]+$/,
preQueryRegEx = /^([^?]+)/;
var fileFromURL = urlString.match(postLastSlashRegEx)[0].match(preQueryRegEx)[0];
// fileFromURL = "photo%2FB%_2.jpeg"
Question:
Is there a way I can combine both regular expressions?
I've tried using capture groups, but haven't been able to produce a working solution.

From my comment
You can use a lookahead to find the "?" and use [^/] to match any non-slash characters.
/[^/]+(?=\?)/
To remove the dependency on the URL needing a "?", you can make the lookahead match a question mark or the end of line indicator (represented by $), but make sure the first glob is non-greedy.
/[^/]+?(?=\?|$)/

You don't have to use regex, you can just use split and substr.
var str = "https://cdnstorage.api.com/v0/b/my-app.com/o/photo%2FB%_2.jpeg?alt=media&token=4e32-a1a2-c48e6c91a2ba".split("?")[0];
var fileName = temp.substr(temp.lastIndexOf('/')+1);
but if regex is important to you, then:
str.match(/[^?]*\/([^?]+)/)[1]

The code using the substring method would look like the following -
var fileFromURL = urlString.substring(urlString.lastIndexOf('/') + 1, urlString.lastIndexOf('?'))

Extract characters in URL after certain character up to certain character

I'm trying to extract certain piece of a URL using regex (JavaScript) and having trouble excluding characters after a certain piece. Here's what I have so far:
URL: http://www.somesite.com/state-de
Using url.match(/\/[^\/]+$/)[0] I can extract the state-de like I want.
However when the URL becomes http://www.somesite.com/state-de?page=r and I do the same regex it pulls everything including the "?page=r" which I don't want. I want to only extract the state-de regardless of whats after it (looks like usually a "?" follows it)

This might work:
var arr = url.split("/")
arr[arr.length - 1].split("?")[0]

I'd recommend reading up on regular expressions in general. What you want to do here is make the regular expression stop when it hits the ? in the URL.
Using capturing groups to select which part of the match that you want might also be useful here.
Example:
url.match(/(\/[^\/?]+)(?:\?.*)?$/)[1]

I avoid overly complex RegExs when possible, so I tend to do this in multiple steps (with .replace()):
var stripped = url.replace(/[?#].*/, ''); // Strips anything after ? or #
You can now do the simpler transform to get the state, e.g.:
var state = stripped.split('/').pop()

If you want do it by regex try this one:
url.match(/https?:\/\/([a-z0-9-]+\.)+[a-z]+\/([a-z0-9_-])\/?(\?.*)?/)[1]
Or you could do it using JQuery:
var url = 'http://www.somesite.com/state-de?page=r#mark4';
// Create a special anchor element, set the URL to it
var a = $('<a>', { href:url } )[1];
console.log(a.hostname);
console.log(a.pathname);
console.log(a.search);
console.log(a.hash);

Regex: Getting content from URL

I want to get "the-game" using regex from URLs like
http://www.somesite.com.domain.webdev.domain.com/en/the-game/another-one/another-one/another-one/
http://www.somesite.com.domain.webdev.domain.com/en/the-game/another-one/another-one/
http://www.somesite.com.domain.webdev.domain.com/en/the-game/another-one/

What parts of the URL could vary and what parts are constant? The following regex will always match whatever is in the slashes following "/en/" - the-game in your example.
(?<=/en/).*?(?=/)
This one will match the contents of the 2nd set of slashes of any URL containing "webdev", assuming the first set of slashes contains a 2 or 3 character language code.
(?<=.*?webdev.*?/.{2,3}/).*?(?=/)
Hopefully you can tweak these examples to accomplish what you're looking for.

var myregexp = /^(?:[^\/]*\/){4}([^\/]+)/;
var match = myregexp.exec(subject);
if (match != null) {
result = match[1];
} else {
result = "";
}
matches whatever lies between the fourth and fifth slash and stores the result in the variable result.

You probably should use some kind of url parsing library rather than resorting to using regex.
In python:
from urlparse import urlparse
url = urlparse('http://www.somesite.com.domain.webdev.domain.com/en/the-game/another-one/another-one/another-one/')
print url.path
Which would yield:
/en/the-game/another-one/another-one/another-one/
From there, you can do simple things like stripping /en/ from the beginning of the path. Otherwise, you're bound to do something wrong with a regular expression. Don't reinvent the wheel!