function updateCounter() {
	var message = document.getElementById('message');
	var inputLength = message.value.length;
	var counter = document.getElementById('counter');
	if (inputLength <= 160) {
		counter.innerHTML = 160 - inputLength;
	} else {
		counter.innerHTML = "0";
	}
	message.value = message.value.slice(0, 160);
}