test.js

var updateEvent = function(obj) {
    chrome.extension.sendMessage({
        action: "updateCurrentVol",
        obj: obj
    }, function (res) {
        console.log(res);    
    });
}

user_data = {
                lastVol : lastVol,
                lastVolURL : lastVolURL, 
                currentVol : currentVol,
                currentVolURL : currentVolURL,
                coverImgURL: coverImgURL,
                title : title,
                site : '8comic'
            }