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Find a way to inject scripts faster than we do it at the moment #1029

ameshkov opened this issue May 28, 2018 · 2 comments


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commented May 28, 2018

We need to find a way to improve the current situation and reliably inject our scripts BEFORE the in-page scripts are executed.

There's no 100% reliable way (relevant feature request:, but we can try some hacks in order to achieve a better result than we have at the moment.

First of all, try figure what Tampermonkey does (as I recall they're using onCommitted just like we do, but I may be wrong).

Here's what I suggest:

  1. Split the injection function into a couple of parts;
  2. Use the async onBeforeRequest listener to prepare scripts to be injected (and save it to some temp cache with -- use tabId and frameId pair as a cache key);
  3. Use both onResponseStarted (unreliable but fast) and onCommitted (reliable but not fast enough) listeners to inject scripts;
  4. Use onCompleted and onErrorOccurred to clean up the cache;
  5. Handle the possibility of duplicate injection in the script;
  6. CSS must be injected in the onCommitted handler only;

@ameshkov ameshkov added this to the 2.10 milestone May 28, 2018


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commented Jul 16, 2018

This feature is not reliable, but for some sites, it should inject scripts faster than inline scripts of the site itself.
In order to check this issue, you should

  1. add user rule'hi')
  2. open site
  3. open developer tools
  4. word hi should fire early than other logs

Also in 2.10 JavaScript rules correctly work for iframes in Firefox


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commented Jul 16, 2018

The real example, when it is required:
add the rule!function/, 'String.fromCharCode');
Expected result - ad script, located in <head>, is aborted:
Add .js|$third-party,,important to see ads(dev tools must be closed)


@zebrum zebrum closed this Aug 13, 2018

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