Injecting custom CSS with content.js [CHROME EXTENSION] is not working-CodePudding

I created a chrome extension for changing default font of some websites.

manifest.json

{
  "name": "Custom Font",
  "version": "0.0.1",
  "description": "A Extension to change default Fonts.",
  "manifest_version": 3,
  "content_scripts": [
    {
      "matches": ["https://dev.to/*", "https://github.com/*"],
      "js": ["main.js"] // content.js
    }
  ]
}

main.js

const head = document.head || document.getElementsByTagName('head')[0];

const link = document.createElement('link');
link.rel = 'stylesheet';

if (window.location.href.includes('https://dev.to')) {
  link.href = chrome.runtime.getURL('devTo.css');
}
if (window.location.href.includes('https://github.com')) {
  link.href = chrome.runtime.getURL('github.css');
}

head.appendChild(link);

but when I try to run above code in mentioned websites it is giving me an error :

GET chrome-extension://invalid/ net::ERR_FAILED

CodePudding user response：

If you want to add the style dynamically from your JavaScript content script (in your Chrome extension manifest v3). You can do it like this:

Adding the stylesheet dynamically is a good idea, if you want to give the user an option to enable/disable it at any time. For example with an options page.

manifest.json

{
  "name": "Inject Style",
  "action": {},
  "manifest_version": 3,
  "version": "0.1",
  "description": "Inject the stylesheet from content script",
  "content_scripts": [
    {
      "matches": ["https://dev.to/*", "https://github.com/*"],
      "js": ["main.js"]
    }
  ],
  "permissions": ["activeTab"],
  "host_permissions": ["<all_urls>"],
  "web_accessible_resources": [
  {
    "resources": [ "devTo.css"],
    "matches": [ "https://dev.to/*" ]
  },
  {
    "resources": [ "github.css"],
    "matches": [ "https://github.com/*" ]
  }]
}

main.js (content script)

function addstylesheet(filename){
  var link = document.createElement("link");
  link.href = chrome.runtime.getURL(filename);
  link.type = "text/css";
  link.rel = "stylesheet";
  document.getElementsByTagName("head")[0].appendChild(link);
}

if(window.location.href.match(/(https:\/\/(.*github\.com\/.*))/i)){
  addstylesheet("github.css");
}else if(window.location.href.match(/(https:\/\/(.*dev\.to\/.*))/i)){
  addstylesheet("devTo.css");
}