I am learning to make chrome extensions. I ran into a problem where context scripts that I want to run, even just alert("test");, are unable to when onload is not activated. This also occurs when you press the back arrow to visit the last visited page. I notice that the url changed, but nothing activates. How do I detect this? If the answer is with service workers, a detailed explanation would be greatly appreciated.
Try using chrome.tabs.onUpdated.addListener((id, change, tab)=>{}). This should run every time the URL changes! Here is a minimalistic example of some code that injects js to a site when the URL changes.
background.js:
// inject code on change
chrome.tabs.onUpdated.addListener((id, change, tab) => {
// inject js file called 'inject.js'
chrome.tabs.executeScript(id, {
file: 'inject.js'
});
});
You can do this by using chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {}). However, this will actually trigger multiple times when a page URL is changed. So you need to add a check for the URL in the changeInfo variable to only trigger once.
manifest.json:
{
"name": "URL change detector",
"description": "detect a URL change in a tab, and inject a script to the page!",
"version": "1.0",
"manifest_version": 3,
"permissions": [
"scripting",
"tabs"
],
"host_permissions": [
"http://*/*",
"https://*/*"
],
"background": {
"service_worker": "background.js"
}
}
background.js:
// function that injects code to a specific tab
function injectScript(tabId) {
chrome.scripting.executeScript(
{
target: {tabId: tabId},
files: ['inject.js'],
}
);
}
// adds a listener to tab change
chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
// check for a URL in the changeInfo parameter (url is only added when it is changed)
if (changeInfo.url) {
// calls the inject function
injectScript(tabId);
}
});
inject.js:
// you can write the code here that you want to inject
alert('Hello world!');