I attempted to create a custom element in a Chrome extension content script but customElements.define is null.
customElements.define('customElement', class extends HTMLElement {
constructor() {
super();
}
...
});
So apparently Chrome doesn't want content scripts to create custom elements. But why? Is it a security risk?
I can't seem to find anything in Chrome's extension guide that says it's not allowed.
I found the solution reading this page but the information was so cumbersome I wanted to write this answer for future readers (I am using Manifest v3)
Firstly, install the polyfill :
npm install #webcomponents/webcomponentsjs -D
Then add the polyfill in your content_scripts block in your manifest file :
"content_scripts": [{
"matches": [ "..." ],
"js": [
"./node_modules/#webcomponents/webcomponentsjs/webcomponents-bundle.js",
"content.js"
]
}]
(important: you have to load it before your content script of course as the polyfill needs to load before you can use it)
Now it should works. Cheers
Note: the customElements feature is implemented in most modern browsers but for some reasons the interface is not available from a content script because the scripts are run in an isolated environment (not sharing the same window object space from the webpage the extension runs in).
As of now custom element can be used in chrome extensions UI. In Popup ui, option page ui and in the content script as well But it requires a polyfill which is this.
https://github.com/GoogleChromeLabs/ProjectVisBug - this is the one big custom element in the chrome extension.
Related
I am creating a chrome extension. I have a small extension which includes CSS, javascript and HTML files. I want to run this extension on any web page, but content_script only allows me to run a script file. When I add css or html file extensions it doesn't work. It doesn't show the HTML page that I created for the extension, just script.js. How can I add and HTML file in content_script?
This is my manifest.json file:
{
"manifest_version":2,
"name":"News Plugin",
"description": "This extension will show you the latest news with headlines and small description",
"version":"1.0",
"browser_action":{
"default_icon":"news_icon.png",
"default_popup":"NewsApp.html"
},
//"chrome_url_overrides":{
//"newtab":"NewsApp.html"
//},
"content_scripts":[
{
"matches":["http://*/*","https://*/*"],
"js":["news.js"],
"html":["news.js"],
"css":["style.js"]
}
],
"permissions":[
"activeTab"
]
}
See https://developer.chrome.com/extensions/content_scripts for the specification of the content_scripts property in manifest.json. There's no "html" property in content_scripts. If it did allow injecting HTML, where would it put it, since the original page already has its own HTML? You can only add Javascript and CSS.
If you want to add HTML to the page, you'll need to do it in your Javascript, using DOM manipulation functions, which allow you to specify where the new elements should go.
Im trying to write a Chrome extension that has a dev tools panel. This extension needs to call functions defined on a property on window in a webpage that I also have made. In other words, the extension is only for my own web page and I control both. Example:
// This script is added in my own webpage application when it loads
window.myTest = () => { /* do something */ }
I want to be able to call the function window.myTest from my Chrome extension. I need to make similar functionality like https://github.com/zalmoxisus/redux-devtools-extension.
It seems that I need to do this by inject script/code from my backend page. I have all working, extension with backend page that gets invoked and I can see that the code that I inject gets called in the page context (testing by console.log gets written to the console output of the page).
Here is my code:
manifest.json
{
"manifest_version": 2,
"name": "MyTest",
"description": "MyTest",
"version": "0.0.1",
"minimum_chrome_version": "10.0",
"devtools_page": "devtools.html",
"background": {
"scripts": ["background.js"]
},
"content_scripts": [{
"matches": ["<all_urls>"],
"js": ["testscript.js"]
}],
"permissions": [
"tabs",
"<all_urls>"
]
}
testscript.js
window.myTest(); // myTest is undefined in the context of the injected script
background.js
// empty, but here to be able to open background page
I also have a pannel that sends a message to the background page when a button is clicked. I know that the panel and sending the message also work. But window.myTest is still undefined.
Edit
Removed the injection from background.js, because I did not use it and have same issue as described.
Finally, I got the specs on this. Mozilla and Chrome follow the same specs for extensions.
Content scripts get a "clean" view of the DOM. This means:
Content scripts cannot see JavaScript variables defined by page
scripts.
If a page script redefines a built-in DOM property, the
content script sees the original version of the property, not the
redefined version.
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Content_scripts
I would like to create a chrome extension which changes my default tab in chrome browser.
Inside the page I will put my favorite websites, which I think I can handle using HTML + CSS. My difficult part is how to make it become a chrome extension because I have never done it before.
Can anyone give me some basic steps which I could start with?
You are looking for what's called Override Pages.
An extension can declare that it supplies a new newtab page. Here's a strictly minimal manifest for it:
{
"manifest_version": 2,
"name": "My awesome New Tab override",
"version": "1.0",
"chrome_url_overrides" : {
"newtab": "newtab.html"
}
}
Then you can use this manifest, together with a newtab.html and required resources, to make a simple extension.
There are many guides past that point; you can see the Learn Basics part of the official docs. Remember you can always ask a new question here if you run into specific implementation questions.
I'm new to extension development, maybe someone has a small example ready for my problem.
I plan a more complicate code (that will execute chromium API functions), but solving this task should help me get started:
I want to create an extension that triggers a popup or alert() (just anyything) based on a website javascript call.
So for example my website has a button, when clicked on the button a javascript with a few parameters is executed.
My extension picks those parameters up and executes APIs (for my example just any popup) based on the parameters.
In my basic example I'd like to trigger some sort of popup/notification with the text supplied by the website javascript.
Also only my website domain should be allowed to trigger that, anything else should be rejected.
I'd really appreciate help.
Here is my "empty" manifest
{
"name": "Special API",
"version": "1.0",
"description": "API demo extension.",
"browser_action":
{
"default_icon": "gears.ico",
"popup": "show_credits.htm"
},
"permissions": [
"http://www.mywebsite.com/"
]
}
Here the example button in my website.com/example
<html>
<body>
<button onClick="extension_do_exec('Hellow world','abcabc')">Execute extension function</button>
</body>
</html>
The approach you described is problematic, bacause javascripts of web-pages, and javascripts of extensions are isolated from each other (there is a concept of isolated world). So it is not possible to get a value "supplied by the website javascript" directly into the extension's javascript. I'd suggest another approach. You possibly could exchange with some values by assigning them as properties to DOM objects. These properties can be accessed from a content script, injected into the web-page. Of course, the content script can determine domain of the page and work as appropriate. As for popups, these are internal pages of an extension, and you should implement some kind of messaging between them and your content script.
I'd like to make a very simple extensions that slightly alters how the Downloads page looks. Changing the History page might be interesting too, but that's for later.
Is there a way to do that?
I tried making a Content Script extension, with "chrome://downloads" as match in manifest.json. Chrome won't allow that and responds with an error when packaging the extension.
Is there another simple way? It has to be simple, because changes would be simple, because all chrome:// pages are built with HTML, JS and CSS.
edit
After trying with background scripts a little...
I can't get chrome.tabs.executeScript to work! I added in background.html:
chrome.browserAction.onClicked.addListener(function(tab) {
alert(this.document.body.innerHTML);
alert(chrome.tabs.executeScript(null, {
code : "document.body.style.backgroundColor = 'red';"
}));
});
And I added this in manifest.json to add a (invisible) 'browser action button':
,"browser_action": {
/* "popup": "background.html",*/
"name": "Alter page"
}
The onClicked event fires both alerts (first is background.html's body, second is undefined). But the code (a string with document.body.style.backgroundColor = 'red';) doesn't execute! And ofcourse there's no debugging for extensions like this =)
Any tips anyone? I'm trying to get a hold of the tab's window.document (not background.html's window.document!). An injected script (that's what chrome.tabs.executeScript is supposed to do) should do that.
PS
I'm stealing from make_page_red/manifest and make_page_red/background.html
The 'extension' I have so far: http://hotblocks.nl/js/downloads.rar
EDIT
I found out what I want to achieve is possible with just CSS. I don't need to inject javascript. Does that make it easier? Does that make it possible? =)
According to this documentation, chrome:// URLs are an invalid scheme so they won't be matched:
A match pattern is essentially a URL that begins with a permitted scheme (http, https, file, or ftp), and that can contain '*' characters.
I would look into using override pages instead.
As requested, here's my extension that can at least load when chrome://downloads is loaded, although as I said, I don't think you can modify the page even if you know that's the page you're viewing.
manifest.json
{
"name": "Test",
"version": "0.0.1",
"background_page": "background.html",
"permissions": [
"tabs"
]
}
background.html
<script>
chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab)
{
if (tab.status == "complete")
{
alert(tab.url);
// should alert 'chrome://downloads' on that page. You can
// check for this url here and then do whatever you want
}
});
</script>
Update: Since Chrome 31 there is an API for extensions that allows access to Chrome's downloads: https://developer.chrome.com/extensions/downloads
There's also an API that allows access to list and manage other installed extensions: https://developer.chrome.com/extensions/management
(Previous Answer)
Unfortunately, there's not currently an API for Chrome extensions to access information about a user's downloads. It's a widely requested feature, though, and there's some discussion among Chrome developers here: http://code.google.com/p/chromium/issues/detail?id=12133
Star the issue if it's a feature that you'd like to see, and you'll receive email updates.
As this page shows, there is no API to override the downloads page... However, there is a way to make a file you have made replace the chrome://downloads/ page whenever it is loaded using javascript in your background page...
chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab){
if(changeInfo.status === "loading"){
if(tab.url === "chrome://downloads/"){
chrome.tabs.update(tab.id, {url: "REPLACEMENT.html"});
}
}
});
Essentially what this does is - As soon as the page chrome://downloads begins loading (using the tabs.onUpdated API), the page is redirected to REPLACEMENT.html (Using tabs.update API)... There is no visible delay in the tab update
as this script is run before the chrome://downloads page begins loading... You can use a similar code in your file by pressing CTRL + U on the downloads page to view and copy its source code