content.js code example

Example 1: google chrome extensions content scripts matches

in your manifest.json:

 "content_scripts": [
   {
     "matches": ["http://*.nytimes.com/*"],
     "css": ["myStyles.css"],
     "js": ["contentScript.js"]
   }
 ],

Example 2: set text of dom element

document.getElementById("myBtn").textContent = 'Hello World';