Google Chrome扩展程序WebRequest拦截

Question

I am trying to create a chrome extension that will convert google scholar endnote file to a citation format.

chrome.webRequest.onBeforeRequest.addListener(function(reqObj){
    if (reqObj.tabId != -1){
        var xhr = new XMLHttpRequest();
        xhr.open("GET", reqObj.url, true);
        xhr.onreadystatechange = function(){
            if(xhr.readyState == 4){
                parseEndnote(xhr.responseText); //Parse the endnote and create the citation
            }
        }
        xhr.send();
        return {redirectUrl : "data:text/plain;charset=utf-8,Citation%20Created"}
    }
},
{urls : ["*://*/scholar.enw*"]}, 
["blocking"]
);

Problem:

I have to redirect to a data url. I would prefer the click action to be cancelled .

Returning {cancel : true} results in the user being redirected to a "This-page-was-blocked-by-an-extension generic chrome page"

Any ideas as to how to work around this one?

Answer 1

The process of following a link goes like this:

1. User performs a click (or keypress) action on the link
2. Event handler code runs for that event
3. The click is successful, and the browser undertakes an HTTP request for the resource
   • the onBeforeRequest listeners run
   • other webRequest listeners run, etc.

You're trying to stop the click event in step 2, but your webRequest code doesn't run until step 3. The very fact that your webRequest code is running at all means that some link-activation event ( click or keypress ) has already succeeded.

You'll need to inject a content script into the page to add event-canceling listeners directly to the links you want to stop (eg, with return false or preventDefault ).