I want to block resources (like JavaScript- or CSS-files), before they are fully loaded. The condition, if resources are blocked, depends on their content. Actually, there is no solution for doing this, or?
What i know: Webextensions are similar to Chrome extensions, so they have also the webRequest.onBeforeRequest listener. The listener allows to block files:
function cancel(requestDetails) {
console.log("Canceling: " + requestDetails.url);
return {cancel: true};
}
chrome.webRequest.onBeforeRequest.addListener(
cancel,
{urls: ["<all_urls>"], types: ["script"]},
["blocking"]
);
Until this point, everything is fine. There should also be the requestBody option, so i can make my decision based on the content of the file. But Mozilla Doc says:
- Firefox does not support the "requestBody" option.
Oh, bad story, not cool. So i need an asynchronous XHR request, to get the URLs data:
function cancel(requestDetails) {
return {cancel: getUrlContent(requestDetails.url, function(result) {
if(condition) { console.log(true); } else { console.log(false); }
})};
}
// asynchron XHR request
function getUrlContent(url, callback) { [...] }
=> This doesn't work. the return {cancel: X}; accepts normal functions, like return {cancel: doSth()};, but no asynchron callbacks. I have no option to "return" the result to the cancel JSON.
In other stackoverflow questions, i read about nsIContentPolicy, which is part of
XPCOM. I didn't found a hint, example or description, how i can use this in the Firefox Webextension environment. Is this possible? And if yes, how?
If both things are not possible, how i can do such an extension? Do i have to use the deprecated XPCOM without Webextension?
