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How should I connect my pages to search and highlight text on current tab?
Currently I have:
What I still don't understand after reading:
What is a content page vs. background/event page?
I know one is constantly running vs injected, but that's as much as I got from the chrome extension manual, I still don't quite understand if the content script/page is seperate from the popup.html for example and what the difference between a script in the popup.html vs content page/script is.
What I know:
I know how to search for text on a page, and replace it or change its style etc. using JS.
I need to read up on the messaging API for Chrome Extensions.
I know I need to know how to use the messaging API, is it going to be required for page search and highlighting?
I don't need a walk through or full answer, just a little help visualizing how Chrome extensions work, or at minimum how I should set mine up in relation to page interaction IE:
search.js content page injected >>>>> popup.html
and maybe a short bit about how injection works in chrome extensions(IE, do I only need to specify that it is content page in manifest.json to have it injected or is there more work to it)/expected behavior?
Apologies for the jumbled thoughts/question/possibly missing the things relevant to my questions while reading the manual.
777
I will start with making the purpose of each kind of page/script more clear.
First is the background page/script. The background script is where your extension lives. It isn't required, but in order to do most extension things, you need one. In it you can set up various event listeners and such depending on what you want it to do. It lives in its own little world and can only interact with other pages and scripts using the chrome.* apis. If you set it up as an event page it works exactly the same except that it unloads when not in use and loads back into memory when it has something to do.
Content scripts refer to injected Javascript and/or css. They are the primary tool used for interacting with web pages. They have very limited access to chrome.* apis, but they have full access to the DOM of the page they are injected into. We will come back to using them in a minute.
Now for Popup pages. Unlike the background script and content script, popups have both a HTML and JS portion. The HTML part is just like any other page, just small and as a overlay popup coming out from the icon. The script portion of it, however, can do all the things the background page does, except that it unloads whenever the popup is closed.
Now that the distinctions are more clear let's move on to what you want to do. It sounds like you want to open the popup, have the user enter text to search for in the current tab, then highlight that text on the page. Since you said that you already know how you plan on highlighting the text, I will leave that part to you.
First to set up our manifest file. For this particular action, we don't need a background script. What we do need is both the "tabs" and "activeTab" permissions. These will enable us to inject our script later. We also need to define the browser action with it's popup. Altogether it would look something like this:
"browser_action": {
"default_icon": "icon.png",
"default_popup": "popup.html"
},
"permissions": [
"tabs", "activeTab"
]
Now in our popup.html file, we can only have markup and css, no inline code at all. We will put it all in our js file and include it. Something like this should work:
<!DOCTYPE html>
<html>
<head>
<script src="popup.js"></script>
</head>
<body>
<input type="text" id="searchText">
<button id="searchButton">Search</button>
</body>
</html>
This is where we come back to the content script stuff. There are two ways to inject a content script, first is to define it in the manifest. This works best when you always want to inject it for a particular set of url's. Second, to use the chrome.tabs.executeScript method to inject it when we need to. That is what we will use.
window.onload = function(){
document.getElementById('searchButton').onclick = searchText;
};
function searchText(){
var search = document.getElementById('searchText').value;
if(search){
chrome.tabs.query({active:true,currentWindow:true},function(tabs){
chrome.tabs.executeScript(tabs[0].id,{file:search.js});
chrome.tabs.sendMessage(tabs[0].id,{method:'search',searchText:search});
});
}
}
With this, we have successfully injected our script and then send the search text to that script. Just make sure that the script is wrapped in a onMessage listener like this:
chrome.runtime.onMessage.addListener(function(message,sender,sendResponse){
// message.searchText is the text that was captured in the popup
// Search/Highlight code goes here
});
And that pretty much sums it up. With that, you should be able to get it working. If something is still not clear let me know and I will fix it.
94
I think what's confusing you is the non-existant concept of a "content page". There is no such thing. What you're likely referring to is a "content script". Let me explain the three main components of an extension:
Background Page
As you said, this is the persistent aspect of a Chrome Extension. Even though it can be HTML page it is never rendered. You simply use it to run JavaScript and other content that stays persistent. The only way to "refresh" the background page is to refresh the extension in the extension manager, or to re-install the extension.
This is most useful for saving information that should remain persistent, such as authentication credentials, or counters that should build up over time. Only use the background page when absolutely necessary, though, because it consumes resources as long as the user is running your extension.
You can add a background script like to manafest file like this:
"background": {
"scripts": [
"background.js"
]
},
Or like this:
"background": {
"page": "background.html"
},
Then simply add background.js to background.html via a typical tag.
Popup
This is what you see when you click the icon on the toolbar. It's simply a popup window with some HTML. It can contain HTML, JavaScript, CSS, and whatever you would put in a normal web page.
Not all extension need a popup window, but many do. For example, your highlight extension may not need a popup if all it's doing is highlighting text on a page. However, if you need to collect a search result (which seems likely) or provide the user with some settings or other UI then a popup is a good way to go about this.
You can add a popup to the manifest file like this:
"browser_action": {
"default_popup": "popup.html"
},
Content script
As I mentioned, this is not a "page" per se -- it a script, or set of scripts. A content script is what you use to infuse JavaScript into pages the user is browser. For example, a user goes to Facebook and a content script could change the background to red. This is almost certainly what you'll need to use to highlight text on a page. Simply infuse some JavaScript and any necessarily libraries to search the page or crawl the dom, and render changes to that page.
You can inject content scripts every time a user opens any URL like this:
"content_scripts": [
{
"matches" : [
"<all_urls>"
],
"js" : [
"content.js"
]
}
],
The above injects "content.js" into "all urls".
You'll also need to add this to the permissions:
"permissions": [
"<all_urls>",
]
You can even add JQuery to the list of content scripts. The nice thing about extensions is that the content scripts are sandboxed, so the version of JQuery you inject will not collide with JQuery on pages the user visits.
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