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setting a variable in javascript to be used in another form

I have form with a Grid (telerik), i think the technology behind it doesnt matter. I let user click on a row in the grid. During the click I extract a value from the Grid with Javascript, like so:
function RadDrillDoubleClick(sender, eventArgs) {
var Code = eventArgs.getDataKeyValue("Status");
if (Code == "In Progress" || Code == "")
{
location.href = "Main1.aspx?mode=edit&DID=" + eventArgs.getDataKeyValue("D_ID");
}
else {
location.href = "Main1.aspx?mode=view&DID=" + eventArgs.getDataKeyValue("D_ID");
}
}
After user has clicked the grid, I call this JS function and send them to correct .aspx page with either VIEW or EDIT mode dependent directly on the Code.
What I'm trying to do is once I get to the Main1.aspx page, I want to be able to continue to hold the CODE value, because when users performs a certain action, I'll need to call a javascript function and use the actual CODE to determine what the user will be able to do.....
var Code = eventArgs.getDataKeyValue("Status");
is there any way I can somehow create like a GLOBAL Variable called
CodeValue
that I can pass around to another form without doing it in the URL?

When the browser navigates to a page, all current JavaScript is unloaded from the browser. This means any functions/variables, etc. will not be accessible on the new page unless you've persisted the value in some way.
Common ways of persisting the value include:
Add it to the query string of the URL the user is navigating to
Save the value to a cookie
Save the value to local/session storage
For your scenario, #1 is probably your best bet (keep in mind the user can have multiple browsers/tabs open to your site).

One way to get the value from URL is like this: on the page Main1.aspx, you add to your JavaScript a function that will run after page loads and that will get what it needs from the current URL
var globalValue; // variable that will receive the value from URL
window.onload = function() {
var thisURL = window.location.href;
globalValue = url.split("?").pop();
// this will store in globalValue everything that comes after the last "?"
// example: if the url is www.site.com/text?value, it will store string "value" to globalValue
};

An Alternative to Data Attribute in Jquery

i have a webpage where user can select one of different packages to buy from a list. Package details are coming from a database.
HTML Code
<div data-package='2346343' class="retail-package">Cost : 10$</div>
<div data-package='5465654' class="retail-package">Cost : 20$</div>
<div data-package='3455675' class="retail-package">Cost : 30$</div>
Jquery Code
$('.retail-package').on('click', function() {
$(this).addClass("selected-package");
var selectedPackage = $(this).data("package");
});
Now above code shows how we(specially i) normally select a particular thing out of a list when clicked, In this procedure, as you can see in HTML Code, i am giving out or showing the pakcageId to users i.e. anyone can do a inspect element in a browser and view or even manipulate the data-package attribute, for safety i do a server side check of selected data.
My Question
Is there a way to hide this data exposure, or is there any other cleaner way to accomplish this, because i have seen people using Angular, Webpack etc able to implement a list selection without giving out or showing any data which can be seen by inspect element feature in a browser.
Note : i am sorry if my question is too basic, if this cannot done using jquery what are other technologies which i can use ?

You may create a Map where keys are arbitrary, auto-incremented identifiers, and values are package numbers:
const idPackageMap = new Map()
// id generator: whenever you call it, "i" is incremented and returned
const id = (() => {
let i = 0
return () => ++i
})()
const addPackage = package =>
idPackageMap.set(id(), package)
addPackage(2346343)
addPackage(5465654)
addPackage(3455675)
console.log('contents: ', [...idPackageMap.entries()])
console.log('package number for id 2: ', idPackageMap.get(2))
Now, when you insert those <div> elements you may set the arbitrary identifier, and when you need to locate the actual package number is just about using Map#get: idPackageMap.get(1) (change 1 with any arbitrary identifier).

Call Functions Based On Query String Using JavaScript

On my web app, the user is asked a question and can choose only one of two answers. Yes or no. A query string is created based on their answer.
The following code carries the query string through the URL of every page:
var navlinks = document.getElementsByClassName("qString");
$(navlinks).prop("href", function() { return this.href + location.search; })
There are only 2 query strings, ?choice=yes and ?choice=no.
Once the user is taken through the app, if they navigate to either park01.html, park02.html, or park03.html from any other page, data will be pulled accordingly via a called function().
Here's my concept in pseudocode:
// I assume I should store specific html pages to a variable
var parkPages = ["park01.html", "park02.html", "park03.html”];
if (user clicks on specified html pages stored in variable) {
and the url contains = ?choice=yes;
Then call these functions: funcA(), funcB(), funcC();
}
else {
the url contains = ?choice=no;
Then call these functions: funcD(), funcE(), funcF();
}
Does the concept make sense? And what does the syntax look like?

If you're simply looking for a concrete translation of your pseudocode into JavaScript, based on your last comment, this should be what you need:
if (location.search === "?choice=yes") {
funcA();
funcB();
funcC();
}
else {
funcD();
funcE();
funcF();
}
Though at this stage, I'd recommend spending less time here and more on instructional/tutorial based websites.

Javascript storing data

Hi I am a beginner web developer and am trying to build the interface of a simple e-commerce site as a personal project.The site has multiple pages with checkboxes.
When someone checks an element
it retrives the price of the element and
stores it in a variable.
But when I go to the next page and click on new checkboxes products the variable automaticly resets to its original state.
How can I save the value of that variable in Javascript?I am using the jQuery library.
EDIT:This is the code I've writen using sessionStorage but it still dosen't work when I move to next page the value is reseted.
How can I wright this code so that i dosen't reset on each page change.All pages on my website use the same script.
$(document).ready(function(){
var total = 0;
$('input.check').click(function(){
if($(this).attr('checked')){
var check = parseInt($(this).parent().children('span').text().substr(1 , 3));
total+=check;
sessionStorage.var_name=0 + total;
alert(sessionStorage.var_name);
}else{
var uncheck = parseInt($(this).parent().children('span').text().substr(1 , 3));
total-=uncheck;
}
})

The syntax for sessionStorage is simple, and it retains it's data until the browser window is closed. It acts exactly like any other javascript object. You can use dot-notation or square bracket notation (required for keys with spaces) to access stored values.
Storing values using sessionStorage
sessionStorage['value key'] = 'value to store';
Using stored values
alert(sessionStorage['value key']); // Alerts "value to store".

You could use localStorage to acomplish this. You'd need to set up a fallback for it, using localStorage however could be done like this:
Reading from storage:
if (localStorage['valueName'] !== undefined) {
input.value = localStorage['valueName'];
}
Writing to storage:
localStorage['valueName'] = input.value;
Here's a jsfiddle example: http://jsfiddle.net/yJjLe/

As already mentioned above you can use sessionStorage or localStorage. Another option available is HTML5 Web Databases
And take a look at this presentation.
Also keep in mind that html5 web storage is not secure as anyone can see your stored data simply from the console.

Variable not updating in script string, yet it updates

Very confused here.
I have a search box which reads a list of school names from my database. When I select a school, the id (from the db) gets put in a hidden textbox.
I also have a search box which reads a list of courses from my database. However, I made the query so that it only reads the courses from the selected school.
It does that, in theory.
I was planning to pass the school id, which I grab from the hidden box, to the search script which in turn passes it to my database query. However, the variable I put my school id in doesn't seem to be updating.. yet it does. Let me explain.
I come on the page. The school for my test account has id 1. The id number in my hidden box is indeed 1. I search for a school which I know has some courses assigned to it: the id number in the box changes to 3.
I have a JS variable called school_id which I declared outside of my $(document).ready. I assume that means it's global (that's what I got taught even though SO told me once it isn't really the correct way to do this. Still have to look into that). I wrote a function which updates this variable when the school search box loses focus:
$("#school").blur(function() {
school_id = $("#school_id").val();
});
A quick javascript:alert(school_id); in my browser bar also shows the updated variable: it is now 3 instead of 1.
Onto the search script part of my page (excerpt of the script):
script:"/profiel/search_richting?json=true&limit=6&id=" + school_id + "&"
As you can see, I pass the school_id variable to the script here. However, what seems to be happening is that it always passes '1', the default variable when the page loads. It simply ignores the updated variable. Does this string get parsed when the page loads? In other words, as soon as the page loads, does it actually say &id=1? That's the only idea I can come up with why it would always pass '1'.
Is there a way to make this variable update in my script string? Or what would be the best way to solve this? I'm probably missing out on something very simple here again, as usual. Thanks a lot.
EDIT
Updated per request. I added a function getTheString as was suggest and I use the value of this function to get the URL. Still doesn't work though, it still seems to be concatenating before I get a chance to update the var. HOWEVER, with this code, my ajax log says id:[object HTMLInputElement], instead of id:1. Not sure what that means.
<script type="text/javascript">
var school_id;
$(document).ready(function() {
$("#school").blur(function() {
school_id = $("#school_id").val();
});
// zoekfunctie
var scholen = {
script:"/profiel/search_school?json=true&limit=6&",
varname:"input",
json:true,
shownoresults:false,
maxresults:6,
callback: function (obj) { document.getElementById('school_id').value = obj.id; }
};
var as_json = new bsn.AutoSuggest('school', scholen);
var richtingen = {
script: getTheString(),
varname:"input",
json:true,
shownoresults:true,
maxresults:6
};
var as_json2 = new bsn.AutoSuggest('studierichting', richtingen);
});
function getTheString() {
return "/profiel/search_richting?json=true&limit=6&id=" + school_id + "&";
}
</script>

This is because the URL is static, it is not updated as the ID changes.
You should update the URL as part of the code you wrote to get the ID:
$("#school").blur(function() {
school_id = $("#school_id").val();
// update URL here ...
});

Aren't you concatenating script:"/profiel/search_richting?json=true&limit=6&id=" + school_id + "&" before the event is fired and the var updated?

Okay. So the problem was my third party plug-in instead of the code I wrote. I fixed this by editing the code of the autoSuggest plugin so it now includes my id field in the AJAX request.
var url = this.oP.script+this.oP.varname+"="+encodeURIComponent(this.sInp)+"&id="+ $("#school_id").val();
Thanks to everyone who tried to help me out!