contentscript.js

function setupInjection (file) {
    var s = document.createElement('script');
    s.src = chrome.extension.getURL(file);
    var container = document.head || document.documentElement
    container.insertBefore(s, container.children[0])
    s.onload = function() {s.remove();};
}

var file = 'inpage.js'
setupInjection (file);

var port = chrome.runtime.connect({name: "contentscript"});
port.postMessage({src: "contentScript",dst:"background"});

port.onMessage.addListener(function(msg) {
    //console.log("port.onMessage: " +JSON.stringify(msg));

    window.postMessage({        //forward msg from background to webpage
        "src": "content",
        "dst": "inpage",
        "data":msg
    }, "*");

});

//just for debug, listen to port disconnect event
port.onDisconnect.addListener(function(message) {
    console.log("Port disconnected: " + JSON.stringify(message))
});


//message from background
chrome.runtime.onMessage.addListener(
    function(request, sender, sendResponse) {
        // console.log(sender.tab ?
        //     "from a content script:" + sender.tab.url :
        //     "from the extension");

        if(request.logo === "nebulas"){
            request.src = "content"
            window.postMessage(request, "*");        //forward msg from background to webpage
            return
        }

        window.postMessage({        //forward msg from background to webpage
            "src": "content",
            "data": request
        }, "*");

    });

// Event listener, msg from web-page
window.addEventListener('message', function(e) {
    //if (e.source != window)
    //    return;

    //first version,
    if(e.data.target === "contentscript") {
        port.postMessage({          //forward msg from webpage to background, [just for compatible]
            src: "contentScript",
            dst: "background",
            data: e.data
        })
    }
    //add nebpay support
    if(e.data.logo === "nebulas" && e.data.src === "nebPay") {  //msg from nebPay
        e.data.src = "content"
        chrome.runtime.sendMessage(e.data, function (response) {
            //console.log("response: " + JSON.stringify(response));
        });
    }

});