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JavaScript/Swift + JavaScriptCore - Possible to ignore undefined variables?

I've got a web scraper-ish set of functions that I'm writing in Swift, and I'm using the JavaScriptCore library to... well, execute some JavaScript. I've scraped a file from the web, but it only has a couple of functions that I'm interested in. However, parts of the file contain things like window or window.currentScript, or new window.WeakMap... these things are unfortunately not defined in JavaScriptCore.
This is one of the errors that I'm getting, for example:
TypeError: undefined is not an object (evaluating 'window.document.currentScript.src.indexOf')
Something I'm attempting to do in the meantime is monkeypatch all of the erroring things, like this:
window={};window.document.currentScript.src={};window.document.currentScript.src.indexOf={}
And prepending this to the JS. However, there must be a better way... right?

What I ended up doing was disregarding these references to window altogether—the functions I needed from the JS file didn't ever reference window or its properties. I did some regex magic (magix?) to extract the definitions of the functions I wanted, and made a new string for just those functions. Then, I gave that string to JSContext.evaluateScript. I hope this helps someone!

Understanding a javascript code from website

I'm trying to understand how a webpage works. When you click a button, they call a function from javascript, with some arguments, just like this <a href="javascript:ShowListing('24343434', 22, '2', '434331')" class="btn">. The function (in an external .js) looks like this:
function ShowListing(id1,id2,id3,id4) {
somecode here
Dialog.Show( id1, assets[id2][id3][id4] );
}
My question is, what's assets? I looked for the declaration of the variable in all the scripts and I couldn't find it. Maybe it's defined in a .php?
Is there any way of knowing the value it has given some specific [ids]?
Thanks!

My question is, what's assets?
A variable containing an object of some sort. We can't tell any more than that from the code you've supplied.
I looked for the declaration of the variable in all the scripts and I couldn't find it. Maybe it's defined in a .php?
It has to be defined by client side JavaScript (unless it is a browser built-in which I don't recognise, but seems highly unlikely given the context it is used in). That JS could be in a .php file.
Is there any way of knowing the value it has given some specific [ids]?
Just about every modern browser has a Developer Tools feature.
Developer Tools come with a JavaScript debugger that lets you set breakpoints.
Set a breakpoint to that line and then you can examine the variables in it using the debugger.
Search terms such as how to use the chrome developer tools debugger will help you learn to use those tools for your browser.

First hit F12 if you're on firefox (i think the same goes for chrome) the console panel should be visible, then add the console.log() and refresh the page to see what is asset use
console.log(assets);
the same goes for the other ids and the value of each array in assets

Re-creating a websites javascript function to be used as a stand alone alternative in tampermonkey

I'm looking for a way to do something that may or may not be possible.
On the site http://hitbox.tv/ there is a javascript function I believe that turns text into images.
For example, using:
emotify.emoticons("",{
"emote": ["http://example.com/emote.png", "channel"],
});
in a tampermonkey script or entering it directly into the chrome console would allow all occurrences of "emote" in the chat to be turned into that image.
If I type "emotify" into the chrome console, I'm given:
function (e,f){return f=f||function(h,j,g){return j=(j+", "+g).replace(/"/g,""").replace(/</g,"<"),'<img src="'+h+'" title="'+j+'" alt="" class="smiley"/>'},e.replace(b,function(j,g,m){var k=0,h=m,l=c[m];if(!l){for(;k<d.length&&!d[k].regexp.test(m);)k++;h=d[k].name,l=c[h]}return l?g+f(l[0],l[1],h,m):j})}
and if I type in "emotify.emoticons" I am given:
function (){var k,m,h,o,l=Array.prototype.slice.call(arguments),n="string"==typeof l[0]?l.shift():"",f="boolean"==typeof l[0]?l.shift():!1,g=l[0],j=[];if(g){f&&(c={},d=[]);for(k in g)c[k]=g[k],c[k][0]=n+c[k][0];for(k in c){if(c[k].length>2){for(m=c[k].slice(2).concat(k),h=m.length;h--;)m[h]=m[h].replace(/(\W)/g,"\\$1");o=m.join("|"),d.push({name:k,regexp:new RegExp("^"+o+"$")})}else o=k.replace(/(\W)/g,"\\$1");j.push(o)}b=new RegExp("(^|\\s)("+j.join("|")+")(?=(?:$|\\s))","g")}return c}
So what I'm wondering is, is there a way to use this code in a tampermonkey script somehow so that in the future, if the code is removed from the website, I could still use the emotify.emoticons function to create standalone emotes?
I really hope this makes sense. If you need any more information, fell free to ask. Any help is greatly appreciated!
-Tom

I might be wrong, but my inclination is that no, you can't - because the full behavior for this code is probably actually executed server-side, not in the web browser.
The images would have to get passed to the server to get circulated to the other people in the chatbox anyway
The function you list just returns a function, which does some (somewhat cryptic!) string operations, and little else, indicating the heavy lifting is done elsewhere.
The reason why you can run it using tampermonkey currently is because the function is defined on hitbox.tv. Defining it in tampermonkey probably won't help, because if hitbox removed it, they would also remove everything that uses it, rendering it useless.
You can do more investigation if you feel like it; http://www.hitbox.tv/dist/hitbox-ui.min.js is the link to their (minified) javascript file that runs the website. Running it through http://jsbeautifier.org/ yields a ~55,000 line long file, however, so unless you know what other variable words to search for, it's going to be impractical to comb through by hand.

Javascript Methodname is replaced with !==

On the server lies a html file with javascript code included.
This javascript code includes a method called something like "CheckObject".
This file works for all users, except one specific (but important).
He gets a javascript error and in his browser sourcode appears something unbelievable:
The methodname "CheckObject" is replaced with "Check!==ect", means the "Obj" of the method name is replaced with !==.
Why could that be?
Hope anybody can help me!
Best regards

If he's using a browser that supports extensions (like Firefox, Chrome, and some others), it's probably worth disabling all of the extensions and seeing if the problem goes away.
If you haven't already, I'd completely clear his cache in case there was a bad page transfer once and the browser is reusing it.
I can't imagine how it would be happening reliably otherwise.

How to help the debugger see my javascript, or how to best refactor my script to help make it debugger-friendly?

I have an ASP.NET MVC project that uses some simple AJAX functionality through jQuery's $.get method like so:
$.get(myUrl, null, function(result) {
$('#myselector').html(result);
});
The amount of content is relatively low here -- usually a single div with a short blurb of text. Sometimes, however, I am also injecting some javascript into the page. At some point when I dynamically include script into content that was itself dynamically added to the page, the script still runs, but it ceases to be available to the debugger. In VS2008, any breakpoints are ignored, and when I use the "debugger" statement, I get a messagebox saying that "no source code is available at this location." This fails both for the VS2008 debugger and the Firebug debugger in Firefox. I have tried both including the script inline in my dynamic content and also referencing a separate js file from this dynamic content -- both ways seemed to result in script that's unavailable to the debugger.
So, my question is twofold:
Is there any way to help the debugger recognize the existence of this script?
If not, what's the best way to include scripts that are used infrequently and in dynamically generated content in a way that is accessible to the debuggers?

I can not comment yet, but I can maybe help answer. As qwerty said, firefox console can be the way to go. I'd recommend going full bar and getting firebug. It hasn't ever missed code in my 3 years using it.
You could also change the way the injected javascript is added and see if that effects the debugger you're using. (I take it you're using Microsoft's IDE?).
In any case, I find the best way to inject javascript for IE is to put it as an appendChild in the head. In the case that isn't viable, the eval function (I hate using it as much as you do) can be used. Here is my AJAX IE fixer code I use. I use it for safari too since it has similar behavior. If you need that too just change the browser condition check (document.all for IE, Safari is navigator.userAgent.toLowerCase() == 'safari';).
function execajaxscripts(obj){
if(document.all){
var scripts = obj.getElementsByTagName('script');
for(var i=0; i<scripts.length; i++){
eval(scripts[i].innerHTML);
}
}
}
I've never used jquery, I preferred prototype then dojo but... I take it that it would look something like this:
$.get(myUrl, null, function(result) {
$('#myselector').html(result);
execajaxscripts(result);
});
The one problem is, eval debug errors may not be caught since it creates another instance of the interpreter. But it is worth trying.. and otherwise. Use a different debugger :D

This might be a long shot, but I don't have access to IE right now to test.
Try naming the anonymous function, e.g.:
$.get(myUrl, null, function anon_temp1(result) {
$('#myselector').html(result);
});
I'm surprised firebug is not catching the 'debugger' statement. I've never had any problems no matter how complicated the JS including method was

If this is javascript embedded within dynmically generated HTML, I can see where that might be a problem since the debugger would not see it in the initial load. I am surprised that you could put it into a seperate .js file and the debugger still failed to see the function.
It seems you could define a function in a seperate static file, nominally "get_and_show" (or whatever, possibly nested in a namespace of sorts) with a parameter of myUrl, and then call the function from the HTML. Why won't that trip the breakpoint (did you try something like this -- the question is unclear as to whether the reference to the .js in the dynamic HTML was just a func call, or the actual script/load reference as well)? Be sure to first load the external script file from a "hard coded" reference in the HTML file? (view source on roboprogs.com/index.html -- loads .js files, then runs a text insertion func)

We use firebug for debug javascript, profile requests, throw logs, etc.
You can download from http://getfirebug.com/
If firebug don't show your javascript source, post some url to test your example case.
I hope I've been of any help!

If you add // # sourceURL=foo.js to the end of the script that you're injecting then it should show up in the list of scripts in firebug and webkit inspector.
jQuery could be patched to do this automatically, but the ticket was rejected.
Here's a related question: Is possible to debug dynamic loading JavaScript by some debugger like WebKit, FireBug or IE8 Developer Tool?