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Javascript Find User

I have the below javascript to get the UserID from a online form. This script will go through IE DOM Explorer to find the valued. But when I run the script, it is totally ignoring my "If" statement. It is just providing a value for "NewAuthUserID", without considering the "if".
(function () {
var NewAuthUserID = "";
var UserId = $('tr.background-highlight:contains("REQUESTER PROFILE") + tr').children('td:contains("User ID:")+td').text();
if ('tr.background-highlight:contains("NEW AUTHORIZED INDIVIDUAL PROFILE:"') {
var NewAuthUserID = $('td:contains("User ID:")+td:eq(2)').text();
};
alert(UserId);
alert(NewAuthUserID)
})();

Firstly, I'd suggest to check out how the if statement works: https://www.w3schools.com/js/js_if_else.asp
You need the if statement conditional to return true or false. Right now you're TRYING to use jquery to select things but even that has a syntax issues. Not only that but once the syntax is fixed it STILL won't do what you're attempting to do because you're putting something that will always evaluate to true as the conditional. That jquery selector just returns a function, not a boolean like it looks like you're intending to do. Try this:
(function(){
var NewAuthUserID = "";
var UserId=$('tr.background-highlight:contains("REQUESTER PROFILE") + tr').children('td:contains("User ID:")+td').text();
if($('tr.background-highlight').text() == "NEW AUTHORIZED INDIVIDUAL PROFILE:")){
var NewAuthUserID=$('td:contains("User ID:")+td:eq(2)').text();
}
alert(UserId);
alert(NewAuthUserID)
})();
Notice how I'm snagging the text that you're trying to test against with jquery and expressing it with a conditional instead? In this manner, it will return the boolean: true/false which is what you need to get the if statement to trigger.
Also if you check your syntax, you were missing the $() wrapper around your if statement, but you have a string that looked like it was trying to snag text via jquery.

I suggest formatting your code a bit, this always helps to debug.
The problem is you are trying to use a jQuery selector in your if statement, but you didn't include the $ to evaluate jQuery. It's just evaluating a string, wich results in TRUE (basically doing this: if(true)), so the code block is executed.
Try this instead:
javascript: (function() {
var NewAuthUserID = "";
var UserId = $('tr.background-highlight:contains("REQUESTER PROFILE") + tr').children('td:contains("User ID:")+td').text();
if ($('tr.background-highlight:contains("NEW AUTHORIZED INDIVIDUAL PROFILE:"').length > 0) {
var NewAuthUserID = $('td:contains("User ID:")+td:eq(2)').text();
};
alert(UserId);
alert(NewAuthUserID)
})();
EDIT: I added the length > 0 check on the returned object. It's possible to accomplish this with OP's code, he was just missing those two pieces. :contains is not the same as .text() ==.

Off topic response:
The way you manage/select your nodes may require a lot of maintanance in the future and is prone to errors.
For example: tr.background-highlight:contains("REQUESTER PROFILE") + tr
In words: Get me the table-row after a table-row with hilighted background, that contains "REQUESTER PROFILE".
What if you'll have to add a row in between them? what if you'll need to select the row, wether it is hilighted or not? what if further rows will be hilighted in the future, so that this selector ain't uniqu anymore? what if the label changes? maybe even the language? ...
In each of these cases you'll have to revisit (potentially all) your jquery selectors, just because some minor layout changed.
That's not very reliable.
Will you remember that when you'll get asked to do these changes? Maybe someone else will have to do these changes, will he/she know what to look for?
Tell me, do you remember the details/implications/quirks of the work you've done a week ago? not to speak about your work from a few months ago.
Better:
Use "unique" identifier to, well, identify your nodes by their role; and I'm not talking about IDs. Unique within their specific context.
The easiest way would be to use css-classes. Annotating the rows/cells so you can select the very same field as $('.ref-requester-provile .ref-user-id')
This is way more reliable and future-proof than your bulky $('tr.background-highlight:contains("REQUESTER PROFILE") + tr').children('td:contains("User ID:")+td') where your JS needs to know every little detail of your template/markup, and needs to be adapted with every little change.
Why did I prepend these classes with ref-? to distinct them from classes that are meant for styling
If you don't need to style these nodes and need these identifyer solely to reference them in your JS, I'd rather use a data-attribute. Why? Let's sum it up with:
performance: when you need to add/remove these marker; avoid unnecessary render-cycles
A cleaner seperation between style and code: classes are primarily for styling, but we don't style here.

Whats the best way to insert content into an HTML document with JavaScript

I was wondering sense there were so many ways to add content dynamically, which way is better.
I know of only of three methods
that add to a body's text node
document.body.innerHTML+="<div>"+myContent+"</div>";
add to the current text node
document.write("<div>"+myContent+"</div>");
and add a whole new node
//case based but for example purpose
var node = document.createElement("div");
node.appendChild(document.createTextNode(myContent));
document.body.appendChild(node);
The third example is obviously more lines. Which is why I'm wondering why I should even consider it. Given download times tend to be worse off then parse times?

document.body.innerHTML+="<div>"+myContent+"</div>";
Destroys any existing event handlers and form data, and creates new elements from the generated source code.
Doesn't safely escape myContent.
document.write("<div>"+myContent+"</div>");
Wipes out the entire document if it is in a closed state
Doesn't safely escape myContent.
var node = document.createElement("div");
node.appendChild(document.createTextNode(myContent));
document.body.appendChild(node);
Verbose, but safe
Option 3 is usually the best.
The third example is obviously more lines. Which is why I'm wondering why I should even consider it. Given download times tend to be worse off then parse times?
Micro-optimisations generally aren't worth the effort. Most of the size difference will be eliminated by HTTP compression anyway.

1) document.body.innerHTML+="<div>"+myContent+"</div>";
Useful when you inserting static HTML (Event Listener not required) in to specific <element>. In this case performance is good.
2) document.write("<div>"+myContent+"</div>");
I will not recommend this way to do. This will overwrite full page.
3) Useful in case Event Listener adding dynamically.
var node = document.createElement("div");
// You can Add Event here.
node.addEventListener("click", function(){ alert("Event Added"); });
node.appendChild(document.createTextNode(myContent));
document.body.appendChild(node);

Greasemonkey, replace every occurence of string every second

i try to figure out a greasemonkey script that replaces every onmousedown on a site with an ondblclick. And i want it to constantly update, like every 1,5 Seconds, because the page refreshes using AJAX.
This is the script i came up with, but it doesn't seem to be working.
window.setInterval(document.body.innerHTML= document.body.innerHTML.replace('onmousedown','ondblclick');,1500);
The page it should work with is internal use only. But a good example would be the google search, where onmousedown is used for the links of the results to swap out the URL before you click it.
I also tried it without the semicolon after the document.body.innerHTML.replace.
I'm really new to JavaScript, but since i'm the only one in the company who can code, this one is stuck with me.
Any help would be appreciated.
Also, a small "side question"
Do i have to use #exclude, or is it enough to only use #include internal.companysite.tld* so it will only work on this site ?

A direct answer: you need to supply a function to setInterval - and it's best to set a variable so that you can later cancel it with clearInterval() if necessary.
function myF(){document.body....;}
var myIntv = setInterval(myF, 1500);
You could also do it using an anonymous function in one line as you're trying to do... do that this way:
var myIntv = setInterval(function(){document.body....;}, 1500);
I wouldn't suggest this as the solution to your problem. What it sounds like you want to do is manipulate the active DOM - not really change the UI. You likely need something like this:
var objs = document.getElementsBy__(); // ById/ByName/etc - depends on which ones you want
for (var i in objs){objs[i].ondblclick = objs[i].onmousedown;objs[i].onmousedown = undefined;} // just an example - but this should convey the basic idea
Even better, if you can use jQuery, then you'll be able to select the proper nodes more easily and manipulate the event handlers in a more manageable way:
$(".class.for.example").each(function(){this.ondblclick = this.onmousedown;this.onmousedown = undefined;}); // just an example - there are multiple ways to set and clear these

Adding Javascript variables to HTML elements

So, I have some code that should do four things:
remove the ".mp4" extension from every title
change my video category
put the same description in all of the videos
put the same keywords in all of the videos
Note: All of this would be done on the YouTube upload page. I'm using Greasemonkey in Mozilla Firefox.
I wrote this, but my question is: how do I change the HTML title in the actual HTML page to the new title (which is a Javascript variable)?
This is my code:
function remove_mp4()
{
var title = document.getElementsByName("title").value;
var new_title = title.replace(title.match(".mp4"), "");
}
function add_description()
{
var description = document.getElementsByName("description").value;
var new_description = "Subscribe."
}
function add_keywords()
{
var keywords = document.getElementsByName("keywords").value;
var new_keywords = prompt("Enter keywords.", "");
}
function change_category()
{
var category = document.getElementsByName("category").value;
var new_category = "<option value="27">Education</option>"
}
remove_mp4();
add_description();
add_keywords();
change_category();
Note: If you see any mistakes in the JavaScript code, please let me know.
Note 2: If you wonder why I stored the current HTML values in variables, that's because I think I will have to use them in order to replace HTML values (I may be wrong).

A lot of things have been covered already, but still i would like to remind you that if you are looking for cross browser compatibility innerHTML won't be enough, as you may need innerText too or textContent to tackle some old versions of IE or even using some other way to modify the content of an element.
As a side note innerHTML is considered from a great majority of people as deprecated though some others still use it. (i'm not here to debate about is it good or not to use it but this is just a little remark for you to checkabout)
Regarding remarks, i would suggest minimizing the number of functions you create by creating some more generic versions for editing or adding purposes, eg you could do the following :
/*
* #param $affectedElements the collection of elements to be changed
* #param $attribute here means the attribute to be added to each of those elements
* #param $attributeValue the value of that attribute
*/
function add($affectedElements, $attribute, $attributeValue){
for(int i=0; i<$affectedElements.length; i++){
($affectedElements[i]).setAttribute($attribute, $attributeValue);
}
}
If you use a global function to do the work for you, not only your coce is gonna be easier to maintain but also you'll avoid fetching for elements in the DOM many many times, which will considerably make your script run faster. For example, in your previous code you fetch the DOM for a set of specific elements before you can add a value to them, in other words everytime your function is executed you'll have to go through the whole DOM to retrieve your elements, while if you just fetch your elements once then store in a var and just pass them to a function that's focusing on adding or changing only, you're clearly avoiding some repetitive tasks to be done.
Concerning the last function i think code is still incomplete, but i would suggest you use the built in methods for manipulating HTMLOption stuff, if i remember well, using plain JavaScript you'll find yourself typing this :
var category = document.getElem.... . options[put-index-here];
//JavaScript also lets you create <option> elements with the Option() constructor
Anyway, my point is that you would better use JavaScript's available methods to do the work instead of relying on innerHTML fpr anything you may need, i know innerHTML is the simplest and fastest way to get your work done, but if i can say it's like if you built a whole HTML page using and tags only instead of using various semantic tags that would help make everything clearer.
As a last point for future use, if you're interested by jQuery, this will give you a different way to manipulate your DOM through CSS selectors in a much more advanced way than plain JavaScript can do.
you can check out this link too :
replacement for innerHTML

I assume that your question is only about the title changing, and not about the rest; also, I assume you mean changing all elements in the document that have "title" as name attribute, and not the document title.
In that case, you could indeed use document.getElementsByName("title").
To handle the name="title" elements, you could do:
titleElems=document.getElementsByName("title");
for(i=0;i<titleElems.length;i++){
titleInner=titleElems[i].innerHTML;
titleElems[i].innerHTML=titleInner.replace(titleInner.match(".mp4"), "");
}
For the name="description" element, use this: (assuming there's only one name="description" element on the page, or you want the first one)
document.getElementsByName("description")[0].value="Subscribe.";
I wasn't really sure about the keywords (I haven't got a YouTube page in front of me right now), so this assumes it's a text field/area just like the description:
document.getElementsByName("keywords")[0].value=prompt("Please enter keywords:","");
Again, based on your question which just sets the .value of the category thingy:
document.getElementsByName("description")[0].value="<option value='27'>Education</option>";
At the last one, though, note that I changed the "27" into '27': you can't put double quotes inside a double-quoted string assuming they're handled just like any other character :)
Did this help a little more? :)

Sry, but your question is not quite clear. What exactly is your HTML title that you are referring to?
If it's an element that you wish to modify, use this :
element.setAttribute('title', 'new-title-here');
If you want to modify the window title (shown in the browser tab), you can do the following :
document.title = "the new title";

You've reading elements from .value property, so you should write back it too:
document.getElementsByName("title").value = new_title

If you are refering to changing text content in an element called title try using innerHTML
var title = document.getElementsByName("title").value;
document.getElementsByName("title").innerHTML = title.replace(title.match(".mp4"), "");
source: https://developer.mozilla.org/en-US/docs/DOM/element.innerHTML

The <title> element is an invisible one, it is only displayed indirectly - in the window or tab title. This means that you want to change whatever is displayed in the window/tab title and not the HTML code itself. You can do this by changing the document.title property:
function remove_mp4()
{
document.title = document.title.replace(title.match(".mp4"), "");
}

conditionals in javascript based on page currently showing

because of some problems with joomla "in-content javascript" I have to give all my js logic to one file, but there are problems with inconsistence of dom elements across my site (it is ajax driven, so there is only one script and various DOMs).
What is the best solution to make some conditionals solving this problem..
Is it checking $(selector).length, or is there any better solution..
And in case of the $(selector).length , is there a way to save this selector to variable (performance issues)
for example some kind of
var selector = ($(selector).length !== 0) ? this : false ;
if(selector) { makeSomething; }
The this is actually pointing to Window object..So is there any way to make it like this without need of reselection?
Thanks

var $obj = $('selector');
if ($obj.length) { makeSomething(); }
Actually, this is only meaningful if you are searching for the existence of a certain element (that might identify a whole page) and running several operations based on that.
If you just want to do something on the elements like
$('selector').append('x');
the condition might be useless, because if the jQuery collection is empty, the methods won't run anyways (as pointed out by #Gary Green).