I've read the message passing page repeatedly and tried multiple variations of it and I'm assuming I'm making a small mistake.
What I'm trying to do: I want to grab the background color of a page with a content script and then send that information to my popup (not a background page; I don't know if that matters) and then allow the popup to (simple example) write that variable in the popup.
Content scripts run in the same process as the webpage (the "tab" process). Popups run in the same process as the background page (the "extension" process).
It sounds like you want the popup to send a request to the content script using chrome.tabs.sendRequest. The content script should be listening for requests using chrome.extension.onRequest.
Or, you might do it the other way around: the content script sends the request to the extension using chrome.extension.sendRequest and the popup listens for requests using chrome.extension.onRequest. When you send a request from a tab to the extension, any page in the extension process (popups or background) can listen for that request.
See the message passing tutorial which includes examples that you can copy and paste.
Related
I'm currently developing an extension that comes in different parts:
- background script (Chrome background.js
- content script (Chrome content-script.js)
- popup script (popup.js and loaded from the iFrame)
- iframe.html (iframe to be loaded when user activate the extension)
It works great except that I lose all the settings/context (used in the popup script to display info in the iframe) when the user change of page or reload the page in the tab.
Technically I want to isolate the extension per tab (each tab can have its own config) but when a user navigate in a same tab the context should be kept.
Question is: what is the best way to achieve that?
I'm thinking about persisting all the context in the content script and reload it when the event chrome.tabs.onUpdated is fired. Is it the right approach?
I recommend you to read about chrome.storage. You can store data there, both background and content script have access to it.
And probably you will need chrome.runtime.sendMessage and chrome.runtime.onMessage to have conversation between background and content. Each time content script runs in a tab it can request background whether this tab have some existing data or not.
I am trying to build a simple chrome extension so that when a form on a webpage in a specific website is populated and the user presses Submit then the data in the form is captured and then some of that data is injected into another form running on a different website.
I have no access to edit the code for either of the forms so a chrome extension seems to be the best way to do this from what I have read.
I would like to know if this is possible and how to go about it
It is possible using Content Scripts, a Background Page, and/or Chrome.storage
You will need Content Scripts on both websites that have the forms. Use the Manifest File correctly to set up which websites to attach which Content Scripts to.
The first Content Script (the one reading the form being filled and submitted) will have to take the values of each form input, triggered by the submit button.
Then you will need to use Message Passing to send a message (containing all the form data) from that Content Script to your Background Page. The data can be held temporarily or saved into chrome.storage by the Background Page.
Then the second form's Content Script also uses Message Passing to request the data from Background Page, which is delivered from temporary holding or retrieved from chrome.storage then sent.
And finally the second Content Script modifies its website's form to fill in the values.
*By other js files, I mean the files you include in popup.html.
The following code works, so why should I use a background script?
Content script
chrome.extension.onMessage.addListener(
function(request, sender, sendResponse) {
//Some code
}
);
Script included in popup.html
chrome.tabs.query({active:true,windowId: chrome.windows.WINDOW_ID_CURRENT},
function(tab) {
chrome.tabs.sendMessage(tab[0].id, {method: "someMethod"},
function(response){
//Some code
});
});
This
Background pages live as long as the Chrome browser is active (and even longer if the "background" permission is set). Popup pages are only active when the badge's popup is open. The popup can only be opened by the user.
The background page's document is never visible, whilst the popup page becomes visible on click of the badge's button.
Besides that, there's no difference between background pages and popup pages. They run in the same extension's process, and have access to the same set of APIs.
If your extension only needs to be active while the popup is active, you don't need a background page. To save the state of the popup, just use the synchronous localStorage or the asynchronous chrome.storage API. When the variables you use are too complex to be stored using either API, a background page may be useful.
One example where the use of a background page is beneficial:
Imagine an extension that downloads a huge text file from a server. The creation of the resource is very resource-intensive for the server. Technically, everything can be done from within the popup. However, offloading the task to the background page allows the user to do other tasks while the file is downloading (if you use a popup only, the download will stop when the user closes the popup).
Though you didn't ask, I'd like to make you aware of event pages. They are similar to background pages, with one difference: Event pages are automatically closed when the extension is idle. In other words, event pages are only active when needed! By doing this, your extension will profit from the advantages of background pages without needlessly wasting the user's memory.
My last example is also a perfect example of when an event page has to be used. Besides doing the http request on behalf of the popup, the background page does nothing. If you use an event page instead of a background page, you get the best of both worlds: the popup page can be closed without interrupting the download, and the extension will not waste memory.
Documentation
Learn more about Background pages and Event pages
"Popup" in this answer refers to the optional panel of the chrome.browserAction or chrome.pageAction API, set by declaring the "default_popup" key in the manifest file, or programatically using the setPopup method.
I am making an extension for chrome. It fetches data from webpages and emails it via local email client. I have a toolbar button which user has to click to invoke the script.
My script works for a few selected urls. I want my toolbar button to change icon based on whether the url is among our list or not. For example for site1 it should be redicon.png and for site2 it should be blueicon.png. I can change button icon using chrome.browserAction.setIcon. But the problem is that this API does not work in content script. It works fine in the background.js file but not in content.js. Kindly tell me how to achieve this.
I know using pageAction instead would do the trick but my client requirement is that the toolbar icon should change rather than appear and disappear.
What you need to read about is message passing. You are right, content scripts have limited chrome API. However, you can contact background page from content script and tell it to execute anything from chrome API for you. First, you need to create a listener on a background page that will be waiting for messages and then send a message from a content script.
Is it possible to catch the request of a page before it is sent out? I would like to check and modify the data sent out. For example if I have a text box on a page and the form was submitted I would like to get to the data of the text box using the extension modify it and then send it on it's way.
If any one can point me in the right direction that would be grate
Chrome has chrome.experimental.webRequest API module which allows to catch web requests before they are sent, but from the docs it doesn't look like you can modify them, just observe.
I think you would be better off injecting a content script to pages and listening to onbeforesubmit event on forms.