background.js

var newtabUrl = "chrome://newtab/"
var created = false;

function checkAndCreate() {
	if (!created) {

		chrome.tabs.query({"currentWindow":true}, (tabs) => {
			console.log(tabs.length - 1);
			console.log(tabs[tabs.length - 1].url);
			if (tabs[tabs.length - 1].url != newtabUrl) {
				chrome.tabs.create({
					active: false,
					selected: false
				}, () => {});
			}
		});
		created = true;
		setTimeout(() => {
			created = false;
		}, 5000);
	}
}

function checkAndDelete(i = -2) {
	chrome.tabs.query({"currentWindow":true}, (tabs) => {
		var tar = tabs[(i >= 0) ? i : tabs.length + i];
		if (tar.url == newtabUrl && !tar.active) {
			chrome.tabs.remove(tar.id, () => {});
		}
	});
}

function removeEnd() {
	chrome.tabs.query({"currentWindow":true}, (tabs) => {
		if (tabs[tabs.length - 1].url == newtabUrl) {
			for (var i = tabs.length - 2; i >= 0; i--) {
				if (tabs[i].url == newtabUrl && !tabs[i].active)
					chrome.tabs.remove(tar.id, () => {});
				else
					break;
			}
		}
	});
}

function removeAll() {
	chrome.tabs.query({"currentWindow":true}, (tabs) => {
		if (tabs[tabs.length - 1].url == newtabUrl) {
			for (var i = tabs.length - 2; i >= 0; i--) {
				if (tabs[i].url == newtabUrl && !tabs[i].active)
					chrome.tabs.remove(tabs[i].id, () => {});
			}
		}
	});
}

checkAndCreate();
removeAll();

chrome.tabs.onUpdated.addListener((tabId, chInfo, tab) => {
	removeAll();
	if (tab.url != newtabUrl) {
		checkAndCreate();
	}
});

chrome.tabs.onCreated.addListener(() => {
	removeAll();
});

chrome.tabs.onRemoved.addListener(() => {
	setTimeout(() => {
		checkAndCreate();
		removeAll();
	}, 5000);
});

chrome.tabs.onMoved.addListener(() => {
	removeAll();
	setTimeout(() => {
		checkAndCreate();
		removeAll();
	}, 1000);
	setTimeout(() => {
		checkAndCreate();
		removeAll();
	}, 5000);
});

chrome.tabs.onDetached.addListener((tabId, detInfo) => {
	setTimeout(() => {
		chrome.tabs.query({
			windowId: detInfo.oldWindowId
		}, (tabs) => {
			if (tabs.length == 1 && tabs[0].url == newtabUrl) {
				chrome.tabs.remove(tabs[0].id, () => {});
			}
		});

	}, 5000);
})