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Hash URL on pageload in jQuery

I really hope to find a solution here.
Need to load specific elements highlighted first on the pages based on url hash.
I have already set up "click" and "hover" functions for these elements. But also need these elements highlighted based on url. What selector should I use?
Basically I need the following scenario to be implemented:
if https://mypage.com#case1 loads
do this
if https://mypage.com#case2 loads
do this

If I understand your question, you can get the URL and do a simple if else statement where you load what you need to based on the URL string.
It could be something like this:
var url = window.location.href; //get url string
if(url == "https://mypage.com#case1"){
//run your case1 code
}else if(url == "https://mypage.com#case2"){
//run your case2 code
}
I'm not sure what your use case is, but you probably want to parse the URL to get the relevant piece or parameter you are looking for.

Javascript regex to replace ampersand in all links href on a page

I've been going through and trying to find an answer to this question that fits my need but either I'm too noob to make other use cases work, or their not specific enough for my case.
Basically I want to use javascript/jQuery to replace any and all ampersands (&) on a web page that may occur in a links href with just the word "and". I've tried a couple different versions of this with no luck
var link = $("a").attr('href');
link.replace(/&/g, "and");
Thank you

Your current code replaces the text of the element within the jQuery object, but does not update the element(s) in the DOM.
You can instead achieve what you need by providing a function to attr() which will be executed against all elements in the matched set. Try this:
$("a").attr('href', function(i, value) {
return value.replace(/&/g, "and");
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
link
link

Sometimes when replacing &, I've found that even though I replaced &, I still have amp;. There is a fix to this:
var newUrl = "#Model.UrlToRedirect".replace(/&/gi, '%').replace(/%amp;/gi, '&');
With this solution you replace & twice and it will work. In my particular problem in an MVC app, window.location.href = #Model.UrlToRedirect, the url was already partially encoded and had a query string. I tried encoding/decoding, using Uri as the C# class, escape(), everything before coming up with this solution. The problem with using my above logic is other things could blow up the query string later. One solution is to put a hidden field or input on the form like this:
<input type="hidden" value="#Model.UrlToRedirect" id="url-redirect" />
then in your javascript:
window.location.href = document.getElementById("url-redirect").value;
in this way, javascript won't take the c# string and change it.

Using JQuery to display a div based upon a content of URL

I'm trying to use jQuery so that when somebody goes to this exact page: www.mysite.com/somedirectory/somesubdirectory divwhite appears and divgrey is hidden. This code works. However, I was wondering if there is someway to write the code so that it checks to see if somesubdirectory is two directories lower than the root level and not dependent if somedirectory is there or not in case somedirectory's name changes.
$(document).ready(function() {
var myvariable = $(location).attr('href');
if(myvariable.indexOf("/somedirectory/somesubdirectory") > -1) {
$("#divgrey").hide();
$("#divwhite").show();
}
else {
j$("#divgrey").show();
$("#divwhite").hide();
}
});

You could use one line of vanilla JavaScript
window.location.pathname.split('/').length
If this number equals 3, the path name contains two slashes and you are in a subdirectory two levels below the root directory, independent of their names.
Note that this assumes that you take care of trailing slashes in the URL in your .htaccess.

How to allow for another index string to run a script

I have no script abilitiy, but i'd like to edit an existing script which is currently restricting the script from running on any page other then the one that has a certain string in the URL.
Here is the snippet of the script which limits it from running
if(location.href.indexOf("MODULE=MESSAGE")>0||location.href.indexOf("/message")>0)
This only allows the script to run on these pages
mysite/2014/home/11609?MODULE=MESSAGE1
and the pages range from Message1 to Message20
mysite/2014/home/11609?MODULE=MESSAGE20
I would like to also allow the script to be loaded and ran on these pages
mysite/2014/options?L=11609&O=247&SEQNO=1&PRINTER=1
where the SEQNO=1 ranges from 1 to SEQNO=20, just like the MESSAGE1-MESSAGE20 do
Can someone show me how i can edit that small snippet of script to allow the SEQNO string found in the url to work also.
Thanks

If you can't just remove the condition altogether (there's not enough context to know if that's an option), you can just add another or condition (||) like so:
if(location.href.indexOf("MODULE=MESSAGE")>0
||location.href.indexOf("/message")>0
||location.href.indexOf("SEQNO=")>0)
Note that the second clause there isn't actually being used in any of your examples, so could potentially be removed. Also note that this isn't actually checking for a number so it isn't restricted to Message1 to Message20 as you suggest. It would match Message21 or even MessageFoo. That may or may not be a problem for you. You can make the conditions as restrictive or as lose as makes sense.

If you just want to check for the existence of "SEQNO", simply duplicate what is being done for "MODULE_MESSAGE".
if(location.href.indexOf("MODULE=MESSAGE")>0 ||
location.href.indexOf("SEQNO=")>0 ||
location.href.indexOf("/message")>0)
If you want to also ensure that "MESSAGE" ends in 1-20, and "SEQNO=" ends in 1-20, you can use a regex.
// create the end part of the regex, which checks for numbers 1-20
var regexEnd = "([1-9]|1[0-9]|20)[^0-9]*$";
// create the individual regexes
var messageRegex = new RegExp("MODULE=MESSAGE" + regexEnd);
var seqnoRegex = new RegExp("SEQNO=" + regexEnd);
// now comes your if statement, using the regex test() function, which returns true if it matches
if(messageRegex.test(location.href) ||
seqnoRegex.test(location.href) ||
location.href.indexOf("/message")>0)

Why does my if condition prevent either clause from executing?

I'm trying to re-write the URLs of a set of links that I select using a jQuery class selector. However, I only wish to re-write the links that don't already have a href attribute specified, so I put in an if/else construct to check for this... However, it's not working. It does work without the if else statement so I'm pretty sure that is where I screwed up. I'm new to both JavaScript and jQuery so sorry if my question is elementary and/or overly obvious.
var url = window.location;
var barTwitter = $("a.shareTwitter").attr('href');
if (barTwitter).val() == "null") {
$("a.barTwitter").attr('href','http://www.twitter.com/home?status='+ url +'');
} else {
$("a.barTwitter").attr('href',barTwitter);
}

if (barTwitter).val() == "null") {
This is syntactically invalid (count the parentheses!). You rather want to do:
if (barTwitter.val() == "null") {
Further, the val() function only works on input elements which are wrapped by jQuery, not on element attribute values which are at end just normal variables. You rather want to compare normal variables against the literal null:
if (barTwitter == null) {

There are actually a few problems with your code... BalusC correctly describes the first one - syntax errors in your if condition - but you should probably consider some of the rest...
I'll start with your code corrected according to BalusC's answer, with comments added to describe what's happening:
var url = window.location; // obtain the URL of the current document
// select the href attribute of the first <a> element with a shareTwitter class
var barTwitter = $("a.shareTwitter").attr('href');
if (barTwitter == null) { // if that attribute was not specified,
// set the attribute of every matching element to a combination of a fixed URL
// and the window location
$("a.barTwitter").attr('href','http://www.twitter.com/home?status='+ url +'');
} else {
// set the attribute of every matching element to that of the first
// matching element
$("a.barTwitter").attr('href',barTwitter);
}
Other issues with your code
Ok... now the problems:
jQuery matches sets - a single selector can potentially match multiple elements. So if there are multiple links on the page with the shareTwitter class, you'll be pulling the href attribute for the first one, but changing all of them. That's probably not what you want, although if there is only a single link with that class then you don't care.
In the else clause, you're not actually modifying the href at all... Unless you have multiple matching links, in which case you'll change all of them such that they have the href of the first one. Again, probably not what you want, although irrelevant if there is only one link... So, in the best-case scenario, the else clause is pointless and could be omitted.
You can actually omit the if/else construct entirely: jQuery allows you to test for the existence of attributes in the selector itself!
You're including the URL of the current page in the querystring of your new, custom URL - however, you're not properly escaping that URL... This could cause problems, as full URLs generally contain characters that are not strictly valid as part of URL querystrings.
Notes on working with JavaScript
A quick aside: if you plan on doing any development using JavaScript, you should obtain some tools. At minimum, install Firebug and familiarize yourself with the use of that and JSLint. The former will inform you of errors when the browser fails to parse or execute your code (in addition to many, many other useful debugging and development tasks), and the latter will check your code for syntax and common style errors: in this case, both tools would have quickly informed you of the initial problems with your code. Instructing you in the proper use of these tools is beyond the scope of this answer, but trust me - you owe it to yourself to take at least a few hours to read up on and play with them.
Toward safer code
Ok, back to the task at hand... Here's how I would re-write your code:
var url = window.location; // obtain the URL of the current document
// escape URL for use in a querystring
url = encodeURIComponent(url);
// select all <a> elements with a shareTwitter class and no href attribute
var twitterLinks = $("a.shareTwitter:not([href])");
// update each selected link with a new, custom link
twitterLinks.attr('href', 'http://www.twitter.com/home?status='+ url +'');
Note that even though this new code accomplishes the same task, it does so while avoiding several potential problems and remaining concise. This is the beauty of jQuery...

firs of all your syntax is screwed up: if (barTwitter).val() == "null") should be if (barTwitter.val() == "null") or if ((barTwitter).val() == "null")
Secondly barTwitter is either going to be a string or null so you cant call val which is a jQuery Object method specific to input elements.
Lastly you probably dont want to compare to null because it possible the value will be an empty string. Thus its better to use length property or some other method. A sample with lenght is below.. but im not sure what attr returns if if ther eis no value... check the docs.
var url = window.location;
var barTwitter = $("a.shareTwitter").attr('href');
if (barTwitter.length < 1) {
$("a.barTwitter").attr('href','http://www.twitter.com/home?status='+ url +'');
} else {
$("a.barTwitter").attr('href',barTwitter);
}