I'm currently developing a chrome extension, that contains background.js and content_scripts.js. In content_scripts, I've added some "event.preventDefault"
in all elements and also added some elements on the page. But when user clicks my extension for the second time, I'd like to "close" my extension and cancel all changes my extensions have done.
Is there a easy way to do that or do I have to treat all changes that I've made individually?
No, without reloading the page, there is no easy way to generically undo all your changes. Yes, if you want all your changes undone, then you have to undo them yourself. There is no magic recording being made of your changes which will back them out for you if your extension is disabled, or you call a particular API.
There are some obvious strategies for doing so:
Remember the changes you made and undo them one by one (undo changes, remove event listeners, etc). What is required depends on what your extension did and the state you desire to leave it in. You can easily send a message to your content script with chrome.tabs.sendMessage() which indicates that it should disable itself and/or back out any changes.
Reload the page
Store the initial state of at least portions of the page and restore it. This may difficult to do, and could be impossible on generic pages. You would have to know all of the event listeners and potentially other state information which has been set by JavaScript in the page.
Try this.
if(localStorage.getItem('firstClick')==='true'){
localStorage.setItem('firstClick', 'false');
chrome.tabs.executeScript(null, {file: "contentscript.js"});
}
else {
localStorage.removeItem('firstClick');
localStorage.set('firstClick', 'true')
}
Related
So, I've got a situation where I want a background and content script to be run everytime the browser extension icon is clicked. The ideal behaviour is that extension icon is clicked, the script runs, and the popup will open, displaying the data that was grabbed by the script (but this should happen quickly, the script runs and gets the data very fast). Since chrome.pageAction.onClicked will not work if there is a default_popup defined in manifest.json, I think this leaves me with two options:
Use default_popup and figure out that the extension icon has been clicked some other way. I found this solution in another stack overflow post, but the workaround is to use default_popup: "popup.html", and then the popup.js that is defined in popup.html will send a message saying that the icon has been clicked, then when background.js receives this message, it executes the script. I implemented this idea and it worked... kinda. The trouble is, the popup will always come up before the script is fully executed, so you can't actually display the data grabbed by the script in the popup until the next click. I'm not sure there's any way to get the behaviour I desire using this method, so on to the next:
The other solution I can possible think of is to use onClicked, and then make the popup come up some other way, besides using default_popup in manifest.json. I'm also not sure if this is possible, I have looked on stackoverflow and haven't found anything similar.
Is the second method possible? Can the first method work somehow?
Your option #1 is correct, I think all that is needed is a loading screen when the user first sees the popup, and add some code that updates the popup as soon as it hears from the backend. Might need to see some code to better help there.
Option #2 will not really work, unless you opened the popup in a new tab (or just made it a whole new HTML page). I say this because there is a note here from the Chrome Dev team they will not support opening a popup unless it is from a user gesture -- https://stackoverflow.com/a/10484764/4875295.
If you wanted to go that route it would probably look something like:
Delete from your manifest.json browser_action.default_popup
In your background script add something like:
chrome.browserAction.onClicked.addListener(() => {
const data = dataMaker();
chrome.tabs.create({
url: `${chrome.runtime.getURL("app.html")}?data=${data}`
});
});
Then in your html file have some JS that reads the query string and updates the page accordingly.
Though, that's a different approach than you asked for and I think your original route may still be the best bet (with some added JS around loading).
I am creating a web app using web socket, which on user closes the tab I will make an API call to the server to clean the user related info in the server, I used onBeforeUnload listener in javascript, but this method also gets triggered during the page refresh.
I need to trigger a method only during the tab or browser close, but not during the page refresh.
I know this question has been asked several times, some solution suggested using cookies will not be helpful in my case
navigator.sendBeacon() method can be used for sending data from browser to server when a tab is closed.
Here is an example:
window.addEventListener("unload", function informServer() {
navigator.sendBeacon("/server-api-to-collect-data", my-data)
})
More information:
https://developer.mozilla.org/en-US/docs/Web/API/Navigator/sendBeacon
As far as I know, you can not listen to actions of browser's tab close or exits. For your application it is an "unload", whatever caused it...
The only thing I could think about is maybe add a listener for keyboard key press (F5), however it doesn't help in case someone refreshed by clicking on the browser's refresh button.
I don't know what is the use case, but most of the things should be done when a page unloads (no matter why) and/or when the page is back up again. So most of the solutions are for situations where your page is loaded again - and then you can determine what was the source of the load and make farther actions, but since you have an option were someone can close and never come back, that might not be the case.
Some solutions for page load up:
You can use Navigation type.
You can check referer.
You can use cookies or other types of browser storage.
I would recommend to rethink about your use case. Maybe you can do whatever you want on load up or leave it on onBeforeUnLoad without knowing the future :)
Bit of background in the problem: I am working on a project that loads most of it's content via api calls in JS. The initial page is built in PHP and delivered ready to use, but every interaction/load after that is just done in JS async and pushed to the "content area" of the html. I'm adding QoL so that you can navigate back to where you were using your history/back/forward button, but in order to do that, every time you navigate using those buttons, I would like to force-refresh the page (for various reasons which I don't think are relevant but am happy to describe if requested).
I'm struggling to understand both pushState and pageShow when used in conjunction. As far as I know, I can use pushState to push new entries to the history object every time it's run, like so:
// Update history
var stateObj = {};
history.pushState(stateObj, response.data.title, uri);
That seems to be working when I run that section of code and check my browser history; a nice neat entry sitting there every time I run it. As far as I know, the title isn't actually supported by any browser, but it doesn't hurt to have it.
My issue occurs when I try to use that newly generated history with the back/forward buttons. As far as I can tell doing some google research, typical browser behavior will not actually reload the page when I press the back button. Herein is where I believe my problem occurs. While navigating to any url fresh will load that specific piece of content into the content area, the site is basically a single page application, loading content into the content area async as it needs it. It doesn't actually change pages. I'm not sure, but I think that is the core problem. I have tried to use several events to "catch" the back/forward behavior:
window.onunload
window.onpageshow
$(window).on("pagehide", function() {})
window.addEventListener("pageshow", function(event) {})
I know several of those are basically the same thing, but I was trying to cover my bases. I have looked around for a solution, and I know that window.onunload is SUPPOSED to override the bfcache (not even sure if that is my problem), but it doesn't seem to fire at all, no matter how many times I navigate between the history.pushState entries. I'm not familiar enough with any of these functions to tell where my problem is. What am I doing wrong?
How can a chrome extension click on a button on active page?
There is banal page on the Web. There is simple element of button type with specific ID on the page. Also there is Chrome extension with a button. I'd like to click to extension button and the button in turn clicks to page button.
var someElement = document.getElementById('someElement');
someElement.addEventListener('click', function () {
// here I'd like to click on a button with specific ID.
});
The very first thing you want to do is to read the Overview page, especially the Architecture part. Read it thoroughly, and it will answer many questions you have.
Your problem can be split into two parts.
How to trigger something with a click on your extension.
How to click something inside the active tab.
Before I proceed, I'll reiterate what wOxxOm said: there's a great small example in the docs that does nearly what you want. But if you want to be someone taught to fish, not given a fish, read on.
How to trigger something with a click on your extension
It depends on what kind of UI you're using; the simplest is a Browser Action button.
Simplest button:
If you add a browser action to the manifest without specifying a popup:
"browser_action": {
"default_icon": { "38": "icon38.png" }
},
then clicking on it will raise chrome.browserAction.onClicked event to your extension's pages. The only page open at any time you need it is a background page, the role of which is usually the central dispatch for extension events. So, you need a background page that listens to that event:
"background": {
"scripts": ["background.js"]
},
and
// background.js
chrome.browserAction.onClicked.addListener(function(tab) {
// Okay, the actual action should go here
// And look, we already have the required Tab object for free!
});
Variations (exercises for the reader):
If you do specify a "default_popup" in your manifest, then chrome.browserAction.onClicked will not trigger. Instead, a small popup page will open with the HTML file you specify; you can add UI/logic there as you wish, the principle will be the same as normal webpages but with Chrome API access, except:
You'll need to query for the current tab yourself.
You'll need to be mindful of Chrome's extension CSP.
In case you run into problems, you need to know how to debug them.
If your extension targets only a few specific pages, consider using Page Actions instead of Browser Actions.
As noted in the documentation, Event pages are preferable to Background pages. In this case, you can use an Event page easily without any side effects, but in general this may require some thinking.
You could inject your own UI into the page itself with Content scripts; this is an advanced topic and will not be covered here.
How to click something inside the active tab
Since you've read the Architecture overview, you already know that the only part of the extension that can interact with the DOM of an open page is a Content script.
Content scripts can either be specified in the manifest (and then they will automatically be injected and ready for you when a matching page is opened), or they can be manually injected into the page.
In your case, you want to do something simple, and only when clicked. This is a perfect job for programmatic injection, so we'll stick with that.
Assuming the solution from the previous section, you are in a context of a background page and already have the current tab as the tab variable:
// background.js
chrome.browserAction.onClicked.addListener(function(tab) {
// Do something with tab
});
Programmatic injection is done with chrome.tabs.executeScript method. At a minimum, you need to specify the tab you want to inject to, and the code that will be run:
// background.js
chrome.browserAction.onClicked.addListener(function(tab) {
chrome.tabs.executeScript(tab.id, {
code: "document.getElementById('#specificId').click()"
});
});
That's not all yet though. The extension must have permissions to execute code in an open tab.
You could use "host permissions" that are defined by a match pattern to give access to specific pages, but remember that we are only triggering it when the user clicks the extension.
For that specific case, there's a special permission "activeTab". It is sufficient to do a lot of things with the currently active tab when the extension is explicitly invoked, and clicking its button is explicit enough.
So, add to manifest:
"permissions": ["activeTab"],
And that should be all you need for this to work.
Extra credit:
While not necessary for this simple purpose, you may want more complicated code than a single line to be executed in the tab. Then it makes sense to use a separate file and invoke executeScript with "file" instead of "code".
Just triggering a click on a button does not require you to directly interact with JavaScript running in the page itself, as DOM events are shared. However, it's important to understand that normally, content scripts can't interact with the page's own scripts, which is called "isolated world". There are ways to bypass it if you really need it, but it's an advanced topic better explained elsewhere.
Sometimes you need the content script to persist, answer some commands and maybe send its own queries to the extension's pages. In that case, it's probably better to auto-inject through the manifest and use Messaging instead of executeScript.
i want to know is there any way we can know browser's events.. like : clicking on BACK button, FORWARD button, REFRESH button by javascript.
These specific browser events are not available as it would be vulnerable to severe privacy violations. Privacy is something browser vendors hold sacred and a key selling (proverbial) point. All browsers allow you to know is when a user enters or leaves your page for which Kamui pointed out the technical details.
Within the same site, it's possible to achieve some browser event tracking using cookies and javascript. For example track wether users click on a hyperlink and label it as a forward event and when a user leaves the page without clicking on a hyperlink it could be one of:
browser url input
back action
javascript location.href replace
The location.href replace can be tracked as well when you have full control over all javascript, just use a helper method with tracking code instead of directly chaning location.href.
That leaves browser url input and the back action. With cookies and request headers (getting the referrer) it is possible to get close to finding out the forward and back events, though not 100%, but pragmatically, 99% sure is good enough.
Figuring out the refresh event is easy with request headers (referrer), if the current url matches the referrrer, it's a refresh event.
Now I offer no code or definite solution, but I outlined what you could do to track back, forward and refresh events within a single domain context. It won't be a quick and easy way to implement it and as far as I know, there's no framework in existance that reliably tracks browser events or even comes close to what I described above.
A more common/lazy technique to achieve something similar is to create a single page app, for which there are many frameworks available. Just google single page app framework, but thats a pretty heavy solution with other implications that I won't go into now.
You can not capture (for example run some piece of code when user presses Back button) them, however, you can direct your pages in history by using:
history.go
history.back
history.forward
More about JS History object.
As #sarfraz says you cannot capture the back and forward button clicks but you could call
window.onbeforeunload = function(){alert("you just tried to leave the page");};
which should be triggered when either the back/forward/refresh buttons are clicked to perform an action, unfortunately you can't tell if they are going back or forward. Please note don't alert a message it's really annoying when trying to exit a page.
EDIT
you can also do this in jQuery if you have it
$(window).unload( function () { alert("Bye now!"); } );