content.js

function sendToBackground(data){
	chrome.runtime.sendMessage(data);
}

//no direct way to send to iframe, send to background and route to iframe from there. 

function initOnLoad()
{
	sendToBackground({from: 'content', message: 'hi from content'});

	//create iframe and inject into page
	var iframe = document.createElement("iframe");
	iframe.src = chrome.extension.getURL('/iframe/hackbar.html?view=hackbar');
	iframe.classList.add("hackbar");
	iframe.id = 'hackbar';
	//add iframe to Twitter page
	document.body.appendChild(iframe);

	console.log('Injected iframe');

	//listen for messages from iframe
	window.addEventListener('message', function(event) {
		if(event.data.from)
		{
			console.log('Content.js received a message from iframe: ');
			console.log(event.data);
		}
	}, false);

	//listen for messages from background
	chrome.extension.onMessage.addListener(function(request, sender, sendResponse){
		if(request.from)
		{
			console.log('Received msg from BG');
			console.log(request);
		}
	});
}

function scheduleInjection()
{
	console.log('Page loaded');
	//wait for 3 sec after page load event for other components to load
	setTimeout(initOnLoad, 3000);
}

window.addEventListener("load", scheduleInjection);