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How to get an id , baseUri from jQuery object and use it as string

I have a Jquery object like the example below
[li#myid.item.fr-hide, prevObject: _.fn.init[1], context: a.link.pjaxload]0: li#myid.item.fr-hidecontext: a.link.pjaxloadlength: 1prevObject: _.fn.init[1]__proto__: _[0]
The object has an arrow pointing down and when i click the arrow , there are some other variable arrows namely 0: li#myid.item.fr-hide,accesskey etc. And when i click the 0, there are some more collections and among which is the baseUri.The baseUri contains a string uri with the part of the string which is myid.
I want to compare and check that object all the time if part of that baseUri example
//www.mydomain.com/myid?l=FR
contains myid . I tried everything possible but because my object is not a string i just count get it going/comparing
i tried.
if(/myid/i.test($active.item.get(0).outerHTML){
}
It failed.
I tried
if(/myid/i.test($active.item.id.outerHTML){
}
It failed. I tried many more that i lost count. Note myid is an element that has id and its id is what i am after. But the id is also contain in the baseUri. Please any help would be appreciated.

I finally get it going. active.item is a jQuery object. Below is what works for me
var $elementid = active.item.get(0).id;
if(active.item) {
if(page.language() === 'FR' && /myid/i.test($elementid)){
//My code
}
}
Another issue i encounter was var $elementid = active.item.get(0).id; passed my element id value to $elementid. However
if(page.language() === 'FR' && /myid/i.test($active.item.get(0).id)){
//My code
}
The above failed and always return false. When i log active.item.get(0).id on the console, it turns out it returns an object not my id . This i am not sure though , looking for a better explanation as well.

Trying to reduce repetition of javascript using a variable

I am trying to reduce the repetition in my code but not having any luck. I reduced the code down to its simplest functionality to try and get it to work.
The idea is to take the last two letters of an id name, as those letters are the same as a previously declared variable and use it to refer to the old variable.
I used the alert to test whether I was getting the right output and the alert window pops up saying "E1". So I am not really sure why it wont work when I try and use it.
E1 = new Audio('audio/E1.ogg');
$('#noteE1').click(function() {
var fileName = this.id.slice(4);
//alert(fileName); used to test output
fileName.play();
$('#note' + fileName).addClass('active');
});
The code block works when I use the original variable E1 instead of fileName. I want to use fileName because I am hoping to have this function work for multiple elements on click, instead of having it repeated for each element.
How can I make this work? What am I missing?
Thanks.

fileName is still a string. JavaScript does not know that you want to use the variable with the same name. You are calling the play() method on a string, which of course does not exist (hence you get an error).
Suggestion:
Store your objects in a table:
var files = {
E1: new Audio('audio/E1.ogg')
};
$('#noteE1').click(function() {
var fileName = this.id.slice(4);
//alert(fileName); used to test output
files[fileName].play();
$('#note' + fileName).addClass('active');
});
Another suggestion:
Instead of using the ID to hold information about the file, consider using HTML5 data attributes:
<div id="#note" data-filename="E1">Something</div>
Then you can get the name with:
var filename = $('#note').data('filename');
This makes your code more flexible. You are not dependent on giving the elements an ID in a specific format.

How do I concatenate a string with a variable?

So I am trying to make a string out of a string and a passed variable(which is a number).
How do I do that?
I have something like this:
function AddBorder(id){
document.getElementById('horseThumb_'+id).className='hand positionLeft'
}
So how do I get that 'horseThumb' and an id into one string?
I tried all the various options, I also googled and besides learning that I can insert a variable in string like this getElementById("horseThumb_{$id}") <-- (didn't work for me, I don't know why) I found nothing useful. So any help would be very appreciated.

Your code is correct. Perhaps your problem is that you are not passing an ID to the AddBorder function, or that an element with that ID does not exist. Or you might be running your function before the element in question is accessible through the browser's DOM.
Since ECMAScript 2015, you can also use template literals (aka template strings):
document.getElementById(`horseThumb_${id}`).className = "hand positionLeft";
To identify the first case or determine the cause of the second case, add these as the first lines inside the function:
alert('ID number: ' + id);
alert('Return value of gEBI: ' + document.getElementById('horseThumb_' + id));
That will open pop-up windows each time the function is called, with the value of id and the return value of document.getElementById. If you get undefined for the ID number pop-up, you are not passing an argument to the function. If the ID does not exist, you would get your (incorrect?) ID number in the first pop-up but get null in the second.
The third case would happen if your web page looks like this, trying to run AddBorder while the page is still loading:
<head>
<title>My Web Page</title>
<script>
function AddBorder(id) {
...
}
AddBorder(42); // Won't work; the page hasn't completely loaded yet!
</script>
</head>
To fix this, put all the code that uses AddBorder inside an onload event handler:
// Can only have one of these per page
window.onload = function() {
...
AddBorder(42);
...
}
// Or can have any number of these on a page
function doWhatever() {
...
AddBorder(42);
...
}
if(window.addEventListener) window.addEventListener('load', doWhatever, false);
else window.attachEvent('onload', doWhatever);

In javascript the "+" operator is used to add numbers or to concatenate strings.
if one of the operands is a string "+" concatenates, and if it is only numbers it adds them.
example:
1+2+3 == 6
"1"+2+3 == "123"

This can happen because java script allows white spaces sometimes if a string is concatenated with a number. try removing the spaces and create a string and then pass it into getElementById.
example:
var str = 'horseThumb_'+id;
str = str.replace(/^\s+|\s+$/g,"");
function AddBorder(id){
document.getElementById(str).className='hand positionLeft'
}

It's just like you did. And I'll give you a small tip for these kind of silly things: just use the browser url box to try js syntax. for example, write this: javascript:alert("test"+5) and you have your answer.
The problem in your code is probably that this element does not exist in your document... maybe it's inside a form or something. You can test this too by writing in the url: javascript:alert(document.horseThumb_5) to check where your mistake is.

Another way to do it simpler using jquery.
sample:
function add(product_id){
// the code to add the product
//updating the div, here I just change the text inside the div.
//You can do anything with jquery, like change style, border etc.
$("#added_"+product_id).html('the product was added to list');
}
Where product_id is the javascript var and$("#added_"+product_id) is a div id concatenated with product_id, the var from function add.
Best Regards!

getting variable/object elements and values in javascript

I'm not sure if I'm using the correct terminology, so please correct me if I'm not.
I've got a javascript variable which holds a group of values like this
var my_variables = {
first_var: 'starting',
second_var: 2,
third_var: 'continue',
forth_var: 'end'
}
Now I'm trying to get these variables in my script, but I don't want to have to check for each one.
Right now i'm doing this
if(my_variables.first_var!=null){
query=query+'&first_var='+my_variables.first_var;
}
if(my_variables.second_var!=null){
query=query+'&second_var='+my_variables.second_var;
}...
I'm hoping there is a simple way to recursively go through the object, but I haven't been able to find how to do that.
Something like
foreach(my_variables.??? as varName){
query=query+'&'+varName+'='+my_variables.varName;
}

Try this:
for(var key in my_variables)
query += '&'+key+'='+encodeURIComponent(my_variables[key]);

for (var varName in my_variables) {
query=query+'&'+varName+'='+my_variables[varName];
}
for (... in ...) is how you write this kind of loop in Javascript. Also use square brackets instead of a period when the field name is a value instead of the actual identifier, like here. Incidentally, I'd also suggest using window.encodeURIComponent if your values might contain arbitrary text.

How to avoid javascript retrieving values from non-existing elements

Update: clarified question (I hope)
Hi.
I'm developing a plugin in Wordpress and I'm outputting elements according to user privileges A and B.
In case of A, I ouput element "Foo".
In case of B, I output element "Bar".
Up till now, I haven't checked if an element exists before I try to retrieve the value.
This of course gives me a javascript error in some browsers (like IE7).
I've looked at using the typeof() function:
if(typeof(element) == 'undefined') {
//do something...
}
I'm also using jQuery. So one solution could be using this:
if ($("#mydiv").length > 0){
// do something here
}
Using the above methods, makes me having to check each element before trying to retrieve any values.
The "ideal" solution would be to get values based on user privileges. E.g:
if (userPriv == A) {
//get values from element 'Foo'
}
This way I can check once, and do the data gathering. The only solutions I can think of are setting the value of a hidden input element or use cookies.
<input type="hidden" id="userPriv" value="A" />
The other solution would be adding a value to the cookie.
setcookie("userPriv", "A");
Unfortunately, this last option gives me a warning message saying that cookie must be set in header (before html output). I think it's because I'm doing this in Wordpress.
I'm looking for opinions on which method is "the best way" to accomplis this.

Forgive me if I'm missing something, but checking for a DOM element in javascript is usually pretty easy.
var elementA = document.getElementById('id_of_a');
var elementB = document.getElementById('id_of_b');
if (elementA) {
//...
} else if (elementB) {
//...
}
The key is the if statement. getElementById will return nothing null if the element is not found, which will evaluate to false in the if statement.
Alternatively, if you don't really want to check for existence of individual DOM elements, can you send the users priv in a hidden input and act on that? That's a cookie free way of sending values clientside. Something like (edited to have jQuery code instead)
<input type="hidden" id="userPriv" value="A" />
...
var priv = $('#userPriv').val();
if (priv == 'A') {
//...
}
I'd still recommend checking for individual elements over checking a hidden input. It seems cleaner to me, more along the unobtrusive lines

You can use object as associative array:
var map = new Object();
map[A.toString()] = new Foo();
map[B.toString()] = new Bar();
In that case is much simpler to check and you will avoid "spaghetti code".