Let's say I have a JSON file stored within my extension called settings.json. I can get the URL of the file using:
chrome.extension.getURL("settings.json");
But now that I have the URL, how do I actually load the contents of that file so I can JSON.parse it and use it? The reason I'm doing this is that there is a server component, and I want to make deployment and testing on multiple servers easier (dev, staging, production, etc.) Alternatively if there's a way to add custom attributes to the manifest.json and access them, that would also work.
If you make your setting.js look like:
var settings = {"param":value,...};
Then you can just include it on a background page and use settings variable:
<script src="settings.js"></script>
If you want to have pure json in your file without assigning it to any variables then you can load it using XMLHttpRequest:
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = handleStateChange; // Implemented elsewhere.
xhr.open("GET", chrome.extension.getURL('/config_resources/config.json'), true);
xhr.send();
or if you included jquery into your project:
$.getJSON(chrome.extension.getURL('/config_resources/config.json'), function(settings) {
//..
});
(btw using chrome.extension.getURL is required only if you are accessing a file from a content script, otherwise you can just use relative path /config_resources/config.json)
I can verify that requesting the resource from an XHR in the background page works as previously described. Just be sure to add 'self' to the connect-src portion of your content_security_policy.
Related
I'm currently developing my first Chrome app that we'll be used as a Kiosk app later.
I'm trying to read a file at the startup of the app, that file is a config file (.json). It contains values that will be passed inside a URL once the app has launched (ie: www.google.com/key=keyValueInTheJsonFile).
I used https://developer.chrome.com/apps/fileSystem (the method "chooseEntry" especially) to be able to read a file, but in my case I would like to directly specify the path/name of the file and not ask the user to select a file. Like that I can pass the values to the redirected URL at the startup.
Any idea of how I could possibly do that?
Thanks!
If your file is in the package you can read it using simple XHR or Fetch.
You can't use web filesystem since it has different purpose and Chrome filesystem (user's FS) won't work here either since it needs a user interaction.
Use function getURL to get a full URL to the resource and then make XHR call:
var rUrl = chrome.runtime.getURL('file.json');
fetch(rUrl).then((response) => {
return response.json();
})
.then((fileContent) => {
// the content
})
.catch((cause) => console.log(cause));
I need to have predefined scripts, accessible from chrome content_script, that could be updated automatically from given URL.
Exactly what i do:
I have content_script.js. Inside it, i`d like to create iframe for current page from predefined html+css+js.Sometimes html or css or js can be changed. I want to avoid updating extension, instead, each time user have internet, he could load fresh html+css+js for further offline usage.
So, how to read and write some internal files within extension from content script (or delegate this task to background script)?
You can use HTML5 Filesystem to have a read/write place for files, or just store it as strings in chrome.storage (with "unlimitedStorage" permission as needed) for later reuse.
This code can then be executed in a content script using executeScript, or, if you enable 'unsafe-eval' for the extension CSP, in the main script (which is dangerous, and should be avoided in most cases).
Note that this Filesystem API has a warning that's it's only supported in Chrome, but that shouldn't be a problem (Firefox / WebExtensions platform explicitly reject self-update mechanisms).
You can do read extension file contents, but you can't write to extension folder since it is sandboxed.
To read an extension file, you can just send Ajax call using chrome.runtime.getURL("filepath") as url
var xhr = new XMLHttpRequest();
xhr.open('GET', chrome.runtime.getURL('your file path'), true);
xhr.onreadystatechange = function() {
if (chr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
var text = xhr.responseText;
// Do what you want using text
}
};
xhr.send();
I am having an issue with the server.mappath method. My current code is:
var imageroot = Server.MapPath("~/Images/Property/");
var foldername = rPropertyId.ToString();
var path = Path.Combine(imageroot, foldername);
When I upload this path into my database, I expect to see the following URL:
/images/property/1/filename.jpg
But what I actually see is this URL:
C:\Users\gavin\Dropbox\My Web Sites\StayInFlorida\Images\Property\1\filename.jpg
How do I get around this? I'm assuming I have to change the MapPath method, but I've tried a few things but I've had no luck.
The Server.MapPath method returns a file system path. What you want is a (relative) URL. Paths and URLs are completely different things. Typically, you need a path if you want to manage files in your server side code, and you need a URL is you are providing access to those files to visitors via hyperlinks. URLs can be constructed from strings:
var url = string.Format("/Images/Property/{0}/{1}", rProprtyId, filename)
I have a chrome extension which monitors the browser in a special way, sending some data to a web-server. In the current configuration this is the localhost. So the content script contains a code like this:
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function(data)...
xhr.open('GET', url, true);
xhr.send();
where url parameter is 'http://localhost/ctrl?params' (or http://127.0.0.1/ctrl?params - it doesn't matter).
Manifest-file contains all necessary permissions for cross-site requests.
The extension works fine on most sites, but on one site I get the error:
XMLHttpRequest cannot load http://localhost/ctrl?params. Origin http://www.thissite.com is not allowed by Access-Control-Allow-Origin.
I've tried several permissions which are proposed here (*://*/*, http://*/*, and <all_urls>), but no one helped to solve the problem.
So, the question is what can be wrong with this specific site (apparently there may be another sites with similar misbehaviour, and I'd like to know the nature of this), and how to fix the error?
(tl;dr: see two possible workarounds at the end of the answer)
This is the series of events that happens, which leads to the behavior that you see:
http://www.wix.com/ begins to load
It has a <script> tag that asynchronously loads the Facebook Connect script:
(function() {
var e = document.createElement('script');
e.type = 'text/javascript';
e.src = document.location.protocol +
'//connect.facebook.net/en_US/all.js';
e.async = true;
document.getElementById('fb-root').appendChild(e);
}());
Once the HTML (but not resources, including the Facebook Connect script) of the wix.com page loads, the DOMContentLoaded event fires. Since your content script uses "run_at" : "document_end", it gets injected and run at this time.
Your content script runs the following code (as best as I can tell, it wants to do the bulk of its work after the load event fires):
window.onload = function() {
// code that eventually does the cross-origin XMLHttpRequest
};
The Facebook Connect script loads, and it has its own load event handler, which it adds with this snippet:
(function() {
var oldonload=window.onload;
window.onload=function(){
// Run new onload code
if(oldonload) {
if(typeof oldonload=='string') {
eval(oldonload);
} else {
oldonload();
}
}
};
})();
(this is the first key part) Since your script set the onload property, oldonload is your script's load handler.
Eventually, all resources are loaded, and the load event handler fires.
Facebook Connect's load handler is run, which run its own code, and then invokes oldonload. (this is the second key part) Since the page is invoking your load handler, it's not running it in your script's isolated world, but in the page's "main world". Only the script's isolated world has cross-origin XMLHttpRequest access, so the request fails.
To see a simplified test case of this, see this page (which mimics http://www.wix.com), which loads this script (which mimics Facebook Connect). I've also put up simplified versions of the content script and extension manifest.
The fact that your load handler ends up running in the "main world" is most likely a manifestation of Chrome bug 87520 (the bug has security implications, so you might not be able to see it).
There are two ways to work around this:
Instead of using "run_at" : "document_end" and a load event handler, you can use the default running time (document_idle, after the document loads) and just have your code run inline.
Instead of adding your load event handler by setting the window.onload property, use window.addEventListener('load', func). That way your event handler will not be visible to the Facebook Connect, so it'll get run in the content script's isolated world.
The access control origin issue you're seeing is likely manifest in the headers for the response (out of your control), rather than the request (under your control).
Access-Control-Allow-Origin is a policy for CORS, set in the header. Using PHP, for example, you use a set of headers like the following to enable CORS:
header('Access-Control-Allow-Origin: http://blah.com');
header('Access-Control-Allow-Credentials: true' );
header('Access-Control-Allow-Headers: Content-Type, Content-Disposition, attachment');
If sounds like that if the server is setting a specific origin in this header, then your Chrome extension is following the directive to allow cross-domain (POST?) requests from only that domain.
Is there a Chrome extension post install hook/API function that will let me perform an action after the plugin is installed or updated?
I would like to perform an action after my extension is installed, and only right after it is installed. This action should only be performed once (post-install or post-update) of the extension.
Update
Some people have proposed setting the version of the extension in localStorage, the problem that I have is that the content script that has access to localStorage is not loaded into the page when the plugin is first installed.
AFAIK after a plugin is installed, and it makes use of a content script injected into the tab/page, the page has to be reloaded.
I don't know how to access localStorage from the background page; localStorage can only be accessed from a content script.
To get the version number from the background page to the content script requires the use of chrome API function to execute scripts:
chrome.tabs.executeScript(null, {code:function_to_execute}, function() { // callback });
However, when you install a plugin, and the page that this plugin needs to inject a content script into is already loaded, it does not inject the content script, you have to reload the page.
update 2
Looking at some of the tips provided in more detail, for the purpose of saving the version number, it is possible to access the localStorage of the background page. However, for what I need to do, which is reload a specific tab at a specific URL (in order to make sure the content script is the newest version) after installing or updating a plugin, it ended up being unnecessary to bother with localStorage.
For the sake of staying on topic, the advice given about writing the version number to localStorage (in the background page) and then checking against the version number in the manifest file is good enough to allow someone to run a script the first time it is installed/or updated.
HowTo
Make manifest file available to the background page (note: this is taken from somewhere else, I don't take credit for it, but I can't remember the source, if you know, let me know and I will add it).
// MAKE MANIFEST FILE AVAILABLE
chrome.manifest = (function() {
var manifestObject = false;
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
manifestObject = JSON.parse(xhr.responseText);
}
};
xhr.open("GET", chrome.extension.getURL('/manifest.json'), false);
try {
xhr.send();
} catch(e) {
console.log('Couldn\'t load manifest.json');
}
return manifestObject;
})();
Now you can access your version number like this: chrome.manifest.version
To write to localStorage just pass it in like so: localStorage['my_plugin_version'] = chrome.manifest.version
You can do this using a background page. When the extension is installed, the background page is opened in the background, and thus executed. To make sure it's not executed every time, simply store a value in localStorage.