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How do I append a query parameter to my URL using Javascript?

I am building a web app and I am using Firebase to store my user's data in Cloud Firestore. There is a page on my web app that allows users to view their documents from Cloud Firestore. I would like to add a query parameter to the end of my URL on view.html so I can take that query parameter value and use it to search for a document.
I have been searching online to find possible solutions. So far I have come across a few videos on the topic, but they haven't been going into the depth I have been needing. For example, this video shows how to add and get query parameters from a URL, but it only shows how to log those changes in the console. How would I make that my URL?
I've also be browsing Stackoverflow for solutions. This Stackoverflow post asks a similar question, however, many of the solutions in the answers causes view.html to reload on a loop. Why would this be, and if this is a possible solution, how would I stop this from happening.
How would I go about appending and fetching URL query parameters in Javascript?

You say you want to do this in javascript, so I assume the page itself is building/modifying a link to either place on the page or go to directly via javascript.
In javascript in the browser there is the URL object, which can build and decompose URLs
let thisPage = new URL(window.location.href);
let thatPage = new URL("https://that.example.com/path/page");
In any case, once you have a URL object you can access the parts of it to read and set the values.
Adding a query parameter uses the searchParams attribute of the URL, where you can add parameters with the .append method — and you don't have to worry about managing the ? and & … the method takes care of that for you.
thisPage.searchParams.append('yourKey', 'someValue');
This demonstrates it live on this page, adding search parameters and displaying the URL at each step:
let here = new URL(window.location.href);
console.log(here);
here.searchParams.append('firstKey', 'theValue');
console.log(here);
here.searchParams.append('key2', 'another');
console.log(here);

I have solved this issue in the simplest way. It slipped my mind that I could link to view.html by adding the search parameter to the URL. Here's what I did:
On index.html where I link to view.html, I created the function openViewer();. I added the parameter to the end of URL href.
function openViewer() {
window.location.href = `view.html?id={docId}`;
}
Then on view.html, I got the parameter using URLSearchParameters like so:
const thisPage = new URL(window.location.href);
var id = thisPage.searchParams.get('id');
console.log(id)
The new URL of the page is now "www.mysite.com/view.html?id=mydocid".

You can try to push state as so in the actual view.html
<script>
const thisPage = new URL(window.location.href);
window.history.pushState("id","id",thisPage);
</script>

How to run javascript based rules against a page?

I would like to run some rules against pages. These rules are essentially functions that check the page for information. They can be simple as in 'check if the page has a title tag' or more complex like 'check if all links on the pages are whitelisted based on example.com/allowed_links.json'.
The rules would be run on the page on-demand only and come from a trusted source.
My first approach has been to create a rule service that sends back an javascript array of rules. All the client then has to do is go over the array and run each function in it. The response is a standard object {rule: [name], pass: [true|false], message: [some message about success/failure]}
Since this is on demand only, we fetch the rules from the service and run 'eval' on it.
EDIT: The response from 'mysite/rules' looks like this
RULESYSTEM.rules.push(function1() {...});
RULESYSTEM.rules.push(function2() {...});
...
const RULESYSTEM = {
rules: [],
};
let rules = fetch('mysite/rules')
let rulesscript = await rules.text();
eval(rulescript)
...
//eval will populate the previously declared rules array.
let pass = true;
for(let i=0; i < RULESYSTEM.rules.length; i++) {
let rule = RULESYSTEM.rules[i];
//This obj has only one property. Get that one.
let result = rule();
pass = pass && result.pass;
}
...
This works perfectly fine. However it is receiving a lot of pushback as 'eval' is considered evil and to be avoided at any cost. The security is not an issue here since the source is within the organization itself and thus trusted.
Are there any other ways to implement a system like this.

It would appear that all you're attempting to do is to retrieve JSON data and transforming it into a javascript object.
fetch('mysite/rules')
.then(res=>res.json())
.then(data=>{
//TODO: handle data which is your object/array
console.log(data)
})
Thus no need for eval. Also you need to remember that fetch returns a promise and that rules.text() and rules.json() also returns a promise. The way you've currently written it won't work anyway.
According to MDN
The json() method of the Body mixin takes a Response stream and reads it to completion. It returns a promise that resolves with the result of parsing the body text as JSON.
To answer your question:
Is it possible to return javascript code as JSON
That's clearly a no, however there are alternatives ! You can simply fetch javacsript as text (as you've done) and programmatically create a script tag, load your javascript text in it and append it to your HTML file.
Or even better, you can simply dynamically create a script tag with the URL of your server endpoint sending javascript and append it to your HTML file.
Something like:
const script = document.createElement("script");
script.onload = function(){
console.log("script loaded");
}
script.src = '/some/url/here';
document.body.appendChild(script);

I am going to add this as an answer. I will use some dummy data you can query based on an endpoint
Route("get-functions")
Response getJSFunctions(List<string> js_to_load){
var options = getData(); //returns a list
var guid = new Guid()
var fp = File.open(guid.toString() + ".js", "w+")
var out = "var fns = [" + options.join("\n") + "];";
fp.write(out);
fp.write(" var runner = options => fns.forEach(fn => fn(options) );");
fp.close()
return new Response({url: guid.toString() + ".js"})
}
Js:
$.json("get-functions", data => {
let script = document.createElement("script");
script.src = data.url;
document.head.appendChild(script)
runner(options);
});
So what is happening is that you build a Temp JS FIle containing all JS Functions you want run, then add that file dynamically to the runtime. Then you have a function which will always be available called runner, which you can immediately call.
Runner will iteratively call each function with a global list of options across the functions, which you can define on the clientside.
Instead of using C#, you can use any serverside or even Javascript if you are using node as your backend. You need DB Access and file creation access on the host machine. You will also want to delete the GUID files ocassionally as they are just one and done use files, so you can delete them all every 5 minutes or something.
I dont have the means right now to create a running sample. I can create something a little later with Python if you like as the backend.

Passing object from one window to another window

I know this question had been asked many times in here, i tried each one of it but it just couldn't work.
I have a website application hosted under https://app.yyy.com, and another one which is basically just a receipt template, which i put inside the mine.com web server. The receipt template has its own script on it, and its URL is https://yyy.com/receipt/receiptTemplate.html. I'm telling all these details because i read that templates that are hosted under the same domain may be subjected to CORS issue when trying to pass data from one window to another.
My requirement is to pass data object from the website application to the receipt template, in which the script will get the object data and render it to the template.
I have the following in the wesbite application script, which is to make a call to fetch data, and open up the receipt template upon successful call. I also tried to attach the data by using window.opener (as suggested by one of the answer that i found in here.
$.get('/getdata', function(data) {
var invoice = window.open('https://yyy.com/receipt/receiptemplate.html');
window.opener.receiptdata = data;
});
And on the receipt script, i have the following
$(document).ready(function(){
var data = window.receiptdata;
generateReceipt(data);
});
But the above couldn't work.
I tried the following with localStorage this time, also suggested by the answer that i found in here..
$.get('/getdata', function(data) {
var invoice = window.open('https://yyy.com/receipt/receiptemplate.html');
localStorage.setItem('receiptdata', data);
});
$(document).ready(function(){
var data = localStorage.getItem('receiptdata');
generateReceipt(data);
});
But didn't work too.
I dunno how else can i pass the object data to the other page... =(

You have a typo to begin with: window in window.opener.receiptdata = data; is your current window, you want to access the window object you just created: invoice.
$.get('/getdata', function(data) {
var invoice = window.open(generateURL(), '');
invoice.receiptdata = data;
}
As a fiddle since StackSnippets won't allow popups.
But for this to work, since you are hosting the two pages on different subdomains, you may need to change their origin:
document.domain = 'yyy.com';
Now, if these were hosted on completely different domains, you would have to use postMessage:
var invoice = window.open('https://yyy.com/receipt/receiptemplate.html');
invoice.postMessage(receiptdata, 'app.yyy');
and in your template
addEventListener('message', e => {
if(e.origin === 'http://app.yyy.com') {
window.receiptdata = e.data;
}
});

Script error: "Unable to get value of the property 'split': Object is null or undefined

I searched around, and couldn't find an answer to my question. I'm very new at coding, and at work, we have an application that current names that are logged in, and what they are doing.
Recently, they have changed from jquery 1.4.1 to jquery 1.8.3. Ever since then, I cannot get the results to process correctly, because of the following error;
"Unable to get value of the property 'split': Object is null or undefined"
I have the code setup to grab the results and split them;
function processAgents(xData, status) {
var avail = xData.responseText.split("|")[0];
var acw = xData.responseText.split("|")[1];
var total = xData.responseText.split("|")[2];
var breaks = xData.responseText.split("|")[3];
var pending = xData.responseText.split("|")[4];
The application is setup to open as an HTA file which opens up the PHP script.
Any help would be appreciated, please let me know if I left anything out!
Thanks!
EDIT 1
I did some more investigating, and it looks like I'm not getting data from my process request. This is how it is currently setup
function updateAgents() {
var ts1 = new Date().getTime();
$.ajax({
url: "http://SERVER/AgentSrc.php?x=" + ts1,
complete: processAgents
I'm not sure if this is processing correctly since they went to jquery 1.8.3.
EDIT 2
So after looking into it more, it doesn't appear that the script is getting the data from the server, even though I have access. If I make a local file and put the information in it, it will pull the information and split it, but if I point to the path of the file on the server, it won't get the information. But the strange thing is, if I run it using jquery 1.4.1, it pulls the data fine, but can't display it. But with 1.8.3, it doesn't allow me to pull it from the server.
thanks again!

This will give some clarity
xData.responseText.toString().split("|")[0];
(split is part of string not jQuery)

Here is a possible explanation: in earlier versions of jQuery, ajax calls returned an xmlHttpRequest (XHR) object. Recent versions return a promise (jqXHR) instead.
See this page for more details.

Using PUT/POST/DELETE with JSONP and jQuery

I am working on creating a RESTful API that supports cross-domain requests, JSON/JSONP support, and the main HTTP method (PUT/GET/POST/DELETE). Now while will be easy to accessing this API through server side code , it would nice to exposed it to javascript. From what I can tell, when doing a JSONP requests with jQuery, it only supports the GET method. Is there a way to do a JSONP request using POST/PUT/DELETE?
Ideally I would like a way to do this from within jQuery (through a plugin if the core does not support this), but I will take a plain javascript solution too. Any links to working code or how to code it would be helpful, thanks.

Actually - there is a way to support POST requests.
And there is no need in a PROXI server - just a small utility HTML page that is described bellow.
Here's how you get Effectively a POST cross-domain call, including attached files and multi-part and all :)
Here first are the steps in understanding the idea, after that - find an implementation sample.
How JSONP of jQuery is implemented, and why doesn't it support POST requests?
While the traditional JSONP is implemented by creating a script element and appending it into the DOM - what results inforcing the browser to fire an HTTP request to retrieve the source for the tag, and then execute it as JavaScript, the HTTP request that the browser fires is simple GET.
What is not limited to GET requests?
A FORM. Submit the FORM while specifing action the cross-domain server.
A FORM tag can be created completely using a script, populated with all fields using script, set all necessary attributes, injected into the DOM, and then submitted - all using script.
But how can we submit a FORM without refreshing the page?
We specify the target the form to an IFRAME in the same page.
An IFRAME can also be created, set, named and injected to the DOM using script.
But How can we hide this work from the user?
We'll contain both FORM and IFRAME in a hidden DIV using style="display:none"
(and here's the most complicated part of the technique, be patient)
But IFRAME from another domain cannot call a callback on it's top-level document. How to overcome that?
Indeed , if a response from FORM submit is a page from another domain, any script communication between the top-level page and the page in the IFRAME results in "access denied". So the server cannot callback using a script. What can the server can do? redirect. The server may redirect to any page - including pages in the same domain as the top-level document - pages that can invoke the callback for us.
How can a server redirect?
two ways:
Using client side script like <Script>location.href = 'some-url'</script>
Using HTTP-Header. See: http://www.webconfs.com/how-to-redirect-a-webpage.php
So I end up with another page? How does it help me?
This is a simple utility page that will be used from all cross-domain calls. Actually, this page is in-fact a kind of a proxi, but it is not a server, but a simple and static HTML page, that anybody with notepad and a browser can use.
All this page has to do is invoke the callback on the top-level document, with the response-data from the server. Client-Side scripting has access to all URL parts, and the server can put it's response there encoded as part of it, as well as the name of the callback that has to be invoked. Means - this page can be a static and HTML page, and does not have to be a dynamic server-side page :)
This utility page will take the information from the URL it runs in - specifically in my implementation bellow - the Query-String parameters (or you can write your own implementation using anchor-ID - i.e the part of a url right to the "#" sign). And since this page is static - it can be even allowed to be cached :)
Won't adding for every POST request a DIV, a SCRIPT and an IFRAME eventually leak memory?
If you leave it in the page - it will. If you clean after you - it will not. All we have to do is give an ID to the DIV that we can use to celan-up the DIV and the FORM and IFRAME inside it whenever the response arrives from the server, or times out.
What do we get?
Effectively a POST cross-domain call, including attached files and multi-part and all :)
What are the limits?
The server response is limited to whatever fits into a redirection.
The server must ALWAYS return a REDIRECT to a POST requests. That include 404 and 500 errors.
Alternatively - create a timeout on the client just before firing the request, so you'll have a chance to detect requests that have not returned.
not everybody can understand all this and all the stages involved. it's a kind of an infrastructure level work, but once you get it running - it rocks :)
Can I use it for PUT and DELETE calls?
FORM tag does not PUT and DELETE.
But that's better then nothing :)
Ok, got the concept. How is it done technically?
What I do is:
I create the DIV, style it as invisible, and append it to the DOM. I also give it an ID that I can clean it up from the DOM after the server response has arrived (the same way JQuery cleans it's JSONP SCRIPT tasgs - but the DIV).
Then I compose a string that contains both IFRAME and FORM - with all attributes, properties and input fields, and inject it into the invisible DIV. it is important to inject this string into the DIV only AFTER the div is in the DOM. If not - it will not work on all browsers.
After that - I obtain a reference to the FORM and submit it.
Just remember one line before that - to set a Timeout callback in case the server does not respond, or responds in a wrong way.
The callback function contains the clean-up code. It is also called by timer in case of a response-timeout (and cleans it's timeout-timer when a server response arrives).
Show me the code!
The code snippet bellow is totally "neutral" on "pure" javascript, and declares whatever utility it needs. Just for simplification of explaining the idea - it all runs on the global scope, however it should be a little more sophisticated...
Organize it in functions as you may and parameterize what you need - but make sure that all parts that need to see each other run on the same scope :)
For this example - assume the client runs on http://samedomain.com and the server runs on http://crossdomain.com.
The script code on the top-level document
//declare the Async-call callback function on the global scope
function myAsyncJSONPCallback(data){
//clean up
var e = document.getElementById(id);
if (e) e.parentNode.removeChild(e);
clearTimeout(timeout);
if (data && data.error){
//handle errors & TIMEOUTS
//...
return;
}
//use data
//...
}
var serverUrl = "http://crossdomain.com/server/page"
, params = { param1 : "value of param 1" //I assume this value to be passed
, param2 : "value of param 2" //here I just declare it...
, callback: "myAsyncJSONPCallback"
}
, clientUtilityUrl = "http://samedomain.com/utils/postResponse.html"
, id = "some-unique-id"// unique Request ID. You can generate it your own way
, div = document.createElement("DIV") //this is where the actual work start!
, HTML = [ "<IFRAME name='ifr_",id,"'></IFRAME>"
, "<form target='ifr_",id,"' method='POST' action='",serverUrl
, "' id='frm_",id,"' enctype='multipart/form-data'>"
]
, each, pval, timeout;
//augment utility func to make the array a "StringBuffer" - see usage bellow
HTML.add = function(){
for (var i =0; i < arguments.length; i++)
this[this.length] = arguments[i];
}
//add rurl to the params object - part of infrastructure work
params.rurl = clientUtilityUrl //ABSOLUTE URL to the utility page must be on
//the SAME DOMAIN as page that makes the request
//add all params to composed string of FORM and IFRAME inside the FORM tag
for(each in params){
pval = params[each].toString().replace(/\"/g,""");//assure: that " mark will not break
HTML.add("<input name='",each,"' value='",pval,"'/>"); // the composed string
}
//close FORM tag in composed string and put all parts together
HTML.add("</form>");
HTML = HTML.join(""); //Now the composed HTML string ready :)
//prepare the DIV
div.id = id; // this ID is used to clean-up once the response has come, or timeout is detected
div.style.display = "none"; //assure the DIV will not influence UI
//TRICKY: append the DIV to the DOM and *ONLY THEN* inject the HTML in it
// for some reason it works in all browsers only this way. Injecting the DIV as part
// of a composed string did not always work for me
document.body.appendChild(div);
div.innerHTML = HTML;
//TRICKY: note that myAsyncJSONPCallback must see the 'timeout' variable
timeout = setTimeout("myAsyncJSONPCallback({error:'TIMEOUT'})",4000);
document.getElementById("frm_"+id+).submit();
The server on the cross-domain
The response from the server is expected to be a REDIRECTION, either by HTTP-Header or by writing a SCRIPT tag. (redirection is better, SCRIPT tag is easier to debug with JS breakpoints).
Here's the example of the header, assuming the rurl value from above
Location: http://samedomain.com/HTML/page?callback=myAsyncJSONPCallback&data=whatever_the_server_has_to_return
Note that
the value of the data argument can be a JavaScript Object-Literal or JSON expression, however it better be url-encoded.
the length of the server response is limited to the length of a URL a browser can process.
Also - in my system the server has a default value for the rurl so that this parameter is optional. But you can do that only if your client-application and server-application are coupled.
APIs to emit redirection header:
http://www.webconfs.com/how-to-redirect-a-webpage.php
Alternatively, you can have the server write as a response the following:
<script>
location.href="http://samedomain.com/HTML/page?callback=myAsyncJSONPCallback&data=whatever_the_server_has_to_return"
</script>
But HTTP-Headers would be considered more clean ;)
The utility page on the same domain as the top-level document
I use the same utility page as rurl for all my post requests: all it does is take the name of the callback and the parameters from the Query-String using client side code, and call it on the parent document. It can do it ONLY when this page runs in the EXACT same domain as the page that fired the request! Important: Unlike cookies - subdomains do not count!! It has to he the exact same domain.
It's also make it more efficient if this utility page contains no references to other resources -including JS libraries. So this page is plain JavaScript. But you can implement it however you like.
Here's the responder page that I use, who's URL is found in the rurl of the POST request (in the example: http://samedomain.com/utils/postResponse.html )
<html><head>
<script type="text/javascript">
//parse and organize all QS parameters in a more comfortable way
var params = {};
if (location.search.length > 1) {
var i, arr = location.search.substr(1).split("&");
for (i = 0; i < arr.length; i++) {
arr[i] = arr[i].split("=");
params[arr[i][0]] = unescape(arr[i][1]);
}
}
//support server answer as JavaScript Object-Literals or JSON:
// evaluate the data expression
try {
eval("params.data = " + params.data);
} catch (e) {
params.data = {error: "server response failed with evaluation error: " + e.message
,data : params.data
}
}
//invoke the callback on the parent
try{
window.parent[ params.callback ](params.data || "no-data-returned");
}catch(e){
//if something went wrong - at least let's learn about it in the
// console (in addition to the timeout)
throw "Problem in passing POST response to host page: \n\n" + e.message;
}
</script>
</head><body></body></html>
It's not much automation and 'ready-made' library like jQuery and involes some 'manual' work - but it has the charm :)
If you're a keen fan of ready-made libraries - you can also check on Dojo Toolkit that when last I checked (about a year ago) - had their own implementation for the same mechanism.
http://dojotoolkit.org/
Good luck buddy, I hope it helps...

Is there a way to do a JSONP request using POST/PUT/DELETE?
No there isn't.

No. Consider what JSONP is: an injection of a new <script> tag in the document. The browser performs a GET request to pull the script pointed to by the src attribute. There's no way to specify any other HTTP verb when doing this.

Rather than banging our heads with JSONP method, that actually won't
support POST method by default, we can go for CORS .That will provide no big changes in the conventional way of programming. By simple Jquery Ajax call we can go with cross domains.
In CORS method, you have to add headers in server side scripting file, or in the server itself(in remote domain), for enabling this access. This is much reliable, since we can prevent/restrict the domains making unwanted calls.
It can be found in detail in wikipedia page.