Cannot read property 'onPageChanged' of undefined

Question

sample extension background.js code

chrome.runtime.onInstalled.addListener(function() {
  chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
    chrome.declarativeContent.onPageChanged.addRules([{
      conditions: [
        // When a page contains a <video> tag...
        new chrome.declarativeContent.PageStateMatcher({
          pageUrl: { hostEquals: 'www.youtube.com'}
        })
      ],
      // ... show the page action.
      actions: [new chrome.declarativeContent.ShowPageAction() ]
    }]);
  });

});

and I got Cannot read property 'onPageChanged' of undefined in console. No problem running the code, why is that happening?

Answer 1

Check that you have added the declarativeContent permission to your manifest.json file.
This will give your extension access to the chrome.declarativeContent API and should resolve your problem.