使用Chrome扩展程序修改或阻止内容JS功能

Question

I need to block writing to LocalStorage. So when the function localstorage.setItem() is called, I need to change it's behaviour or block. I have my content.js in "content_scripts" of manifest

Here are possible ways (I can't find anything on all of them):

1) Event handler of storage change

I've tried

window.addEventListener('storage', function (event) {
    console.log("storage event occured here");
});

But I need detection of function call in the same tab (through extension).

2) Override system function localstorage.setItem()

It works if I will write in console

localStorage.setItem = function(){
    console.log('modified');
  }

But not if in content.js

Also tried to add to manifest "run_at" : "document_start" for content_scripts

3) Event handler of setItem function call

Is it possible to set trigger/handler for custom function call? I know handlers like click, mouseover.. but on function calls - not.

Answer 1

The answer is to inject script file through contents script. Thanks to wOxxOm

content.js

var inj = document.createElement('script');
inj.src = chrome.runtime.getURL('blockaccess.js');
inj.onload = function() {
    this.remove();
};
(document.head || document.documentElement).appendChild(inj);

blockaccess.js

Storage.setItem = localStorage.setItem = sessionStorage.setItem = function(){
  console.log('Blocked Storage setItem()');
}