It was because the website sends many responses, and this code will see another request other than I want, then detach the debugger so I can't get the result.

To solve this, just use a single debugger and do not detach it, or only detach when it's safe to.

var gAttached = false;

var gRequests = [];

var gObjects = [];



chrome.debugger.onEvent.addListener(function (source, method, params) {

        if (method == "Network.requestWillBeSent") {

            // If we see a url need to be handled, push it into index queue

            var rUrl = params.request.url;

            if (getTarget(rUrl) >= 0) {

                gRequests.push(rUrl);

            }

        }

        if (method == "Network.responseReceived") {

            // We get its request id here, write it down to object queue

            var eUrl = params.response.url;

            var target = getTarget(eUrl);

            if (target >= 0) {

                gObjects.push({

                    requestId: params.requestId,

                    target: target,

                    url: eUrl

                });

            }

        }

        if (method == "Network.loadingFinished" && gObjects.length > 0) {

            // Pop out the request object from both object queue and request queue

            var requestId = params.requestId;

            var object = null;

            for (var o in gObjects) {

                if (requestId == gObjects[o].requestId) {

                    object = gObjects.splice(o, 1)[0];

                    break;

                }

            }

            // Usually loadingFinished will be immediately after responseReceived

            if (object == null) {

                console.log('Failed!!');

                return;

            }

            gRequests.splice(gRequests.indexOf(object.url), 1);

            chrome.debugger.sendCommand(

                source,

                "Network.getResponseBody",

                {"requestId": requestId},

                function (response) {

                    if (response) {

                        dispatch(source.tabId, object.target, JSON.parse(response.body));

                    } else {

                        console.log("Empty response for " + object.url);

                    }

                    // If we don't have any request waiting for response, re-attach debugger

                    // since without this step it will lead to memory leak.

                    if (gRequests.length == 0) {

                        chrome.debugger.detach({

                            tabId: source.tabId

                        }, function () {

                            chrome.debugger.attach({

                                tabId: source.tabId

                            }, "1.0", function () {

                                chrome.debugger.sendCommand({

                                    tabId: source.tabId

                                }, "Network.enable");

                            });

                        });

                    }

                });

        }

    }

);



var initialListener = function (details) {

    if (gAttached) return;  // Only need once at the very first request, so block all following requests

    var tabId = details.tabId;

    if (tabId > 0) {

        gAttached = true;

        chrome.debugger.attach({

            tabId: tabId

        }, "1.0", function () {

            chrome.debugger.sendCommand({

                tabId: tabId

            }, "Network.enable");

        });

        // Remove self since the debugger is attached already

        chrome.webRequest.onBeforeRequest.removeListener(initialListener);

    }

};



// Attach debugger on startup

chrome.webRequest.onBeforeRequest.addListener(initialListener, {urls: ["<all_urls>"]}, ["blocking"]);



// Filter if the url is what we want

function getTarget(url) {

    for (var i in TARGETS) {

        var target = TARGETS[i];

        if (url.match(target.url)) {

            return i;

        }

    }

    return -1;

}



const TARGETS = [

    {url: '/path1', desc: 'target1'},

    {url: '/path2', desc: 'target2'}

]