content.js

let images = document.getElementsByTagName("img");
let targetImage = images[Math.floor(Math.random() * images.length)];
let targetImageSource = targetImage.src;
let alreadyFound = false;

chrome.storage.sync.get('urlList', function(result) {
    let urlList = result.urlList || [];

    if(!urlList.includes(window.location.origin)) {
        targetImage.addEventListener('mouseenter', function() {
                targetImage.src = chrome.runtime.getURL('images/kevin.png');
                if(!alreadyFound){
                    alreadyFound = true;

                    chrome.storage.sync.get('counter', function(result) {
                        var value = result.counter;

                        if(value == undefined){
                            value = 0;
                        } else {
                            value += 1;
                        }

                        chrome.storage.sync.set({ 'counter': value });
                    });
                }
            });

            targetImage.addEventListener('mouseleave', function() {
                targetImage.src = targetImageSource
            });
    }
});