index.js

const ul = document.querySelector('ul'),
	form = document.querySelector('.js_'),
	input = document.querySelector('input');
//let count = 4;

check_hanguel = /[ㄱ-ㅎ|ㅏ-ㅣ|가-힣]/;

const list_of_han = ['조용히 해', '치킨이나 먹어', '군대나 가',  '배고파', '살이나 빼', '시끄러워' ];

function receiving(text) {
	console.log(text);
	let li = document.createElement('li');
	li.classList.add('incoming-message');
	li.classList.add('message');
	let img = document.createElement('img');
	img.src = 'images/avatar.jpg';
	img.classList.add('m-avatar');
	img.classList.add('message__avatar');
	let div = document.createElement('div');
	div.classList.add('message__content');
	let span1 = document.createElement('span');
	span1.classList.add('message__author');
	span1.innerText = 'Anna';
	let span2 = document.createElement('span');
	span2.classList.add('message__bubble');
	span2.innerText = text;
	div.appendChild(span1);
	div.appendChild(span2);
	li.appendChild(img);
	li.appendChild(div);
	ul.appendChild(li);
}

function sendmessage(event) {
	event.preventDefault();
	console.log(input.value);

	let li = document.createElement('li');
	li.classList.add('sent-message');
	li.classList.add('message');
	let div = document.createElement('div');
	div.classList.add('message__content');
	let span = document.createElement('span');
	span.classList.add('message__bubble');
	span.innerText = input.value;
	div.appendChild(span);
	li.appendChild(div);
	ul.appendChild(li);

	if (check_hanguel.test(input.value)) {
		if (input.value.indexOf('공부') !== -1) {
			console.log(Math.random(0, list_of_han.length));
			console.log(list_of_han.length);
			num = Number.parseInt(Math.random() * list_of_han.length);
			setTimeout(receiving, 1500, list_of_han[num]);
		} else if (input.value.indexOf('밥') !== -1) {
			setTimeout(receiving, 1500, '나 안배고파');
		} else if (input.value.indexOf('?') !== -1) {
			setTimeout(receiving, 1500, '잘몰라. 대답하기 귀찮아.');
		} else {
			setTimeout(receiving, 1500, 'ㅎㅎ');
		}
	} else {
		setTimeout(receiving, 1500, '영어 못하면서 잘하는척 하지마');
	}

	//receiving(input.value);
	input.value = '';
}

function init() {
	form.addEventListener('submit', sendmessage);
}

init();