JS Алгоритм добавления цифр в массив

let task, tasks, task__close; 
let add__button = document.querySelector('.add__button'); 
let add__input = document.querySelector('.add__input'); 
let arr = []; 
 
function addElem() { 
	if (add__input.value === '') { 
		return false; 
	} 
	let block = document.createElement('div'); 
	let taskId; 
	tasks = document.querySelector('.tasks'); 
	task = document.querySelectorAll('.task'); 
	block.className = 'task'; 
	for (let i = 0; i < task.length; i++) { 
		for (let j = 0; j < task.length; j++) { 
			if (task[i].getAttribute('data-id') ==  
			task[j].getAttribute('data-id')) { 
				arr.push(task[i].getAttribute('data-id')); 
			} 
		} 
	} 
	block.setAttribute('data-id', task.length); 
	block.innerHTML = '<div class="task__close"></div>'; 
	block.innerHTML += add__input.value; 
	tasks.prepend(block); 
	task__close = document.querySelector('.task__close'); 
	add__input.value = ''; 
	startClose(); 
} // function addElem() 
 
function startClose() { 
	task__close = document.querySelectorAll('.task__close'); 
	for (let i = 0; i < task__close.length; i++) { 
		task__close[i].addEventListener('click', (event) => { 
			event.path[1].remove(); 
		}); 
	} 
} // function startClose() 
 
add__button.addEventListener('click', () => { 
	addElem(); 
}); 
 
add__input.addEventListener('keydown', (event) => { 
	if (event.code == 'Enter' || event.keyCode == '13' || event.key == 'Enter') { 
		addElem(); 
	} 
}); 
 
startClose();

@import url('https://fonts.googleapis.com/css?family=Open+Sans:400,700&display=swap'); 
 
*, *:before, *:after { 
	-webkit-box-sizing: border-box; 
	-moz-box-sizing: border-box; 
	box-sizing: border-box; 
} 
 
html{ 
	scroll-behavior: smooth; 
} 
 
body { 
	margin: 0; 
	padding: 0; 
	font-size: 16px; 
	font-family: 'Open Sans', sans-serif; 
	color: black; 
} 
 
h1, h2, h3, h4, h5, h6, ul { 
	margin: 0; 
} 
 
ul { 
	list-style: none; 
} 
 
img { 
	display: block; 
	max-width: 100%; 
	height: auto; 
} 
 
.container { 
	max-width: 1100px; 
	width: 100%; 
	margin: 0 auto; 
} 
 
.container.fluid { 
	max-width: 100%;	 
} 
 
.spheres { 
	display: -webkit-flex; 
	display: -moz-flex; 
	display: -ms-flex; 
	display: -o-flex; 
	display: flex; 
} 
 
.sphere { 
	border-right: 1px solid black; 
	flex-grow: 1; 
	padding: 15px 0; 
} 
 
.sphere:first-child { 
	border-left: 1px solid black; 
} 
 
.sphere	 .svg__icon { 
	max-width: 70px; 
	margin: 0 auto; 
} 
 
.sphere	 .svg__icon img { 
	width: 100%; 
} 
 
.sphere__title { 
	text-align: center; 
	margin-top: 10px; 
	font-size: 20px; 
} 
 
.add { 
	background-color: #46a049; 
	padding: 25px 0; 
} 
 
.add__title { 
	font-size: 22px; 
	text-align: center; 
	color: white; 
} 
 
.add__input-wrapper { 
	position: relative; 
	max-width: 500px; 
	margin: 10px auto 0; 
	padding: 0 15px; 
} 
 
.add__input { 
	outline: 0; 
	font-family: inherit; 
	font-size: inherit; 
	border: 1px solid white; 
	display: block; 
	border-radius: 5px; 
	padding: 7px 55px 7px 20px; 
	width: 100%; 
} 
 
.add__button { 
	position: absolute; 
	top: 50%; 
	right:15px; 
	transform: translate(0, -50%); 
	width: 50px; 
	height: 50px; 
} 
 
.add__button:before { 
	position: absolute; 
	display: block; 
	content: ''; 
	top: 50%; 
	transform: translate(-40%, -50%) rotate(90deg); 
	width: 2px; 
	background-color: #91a8c4; 
	height: 20px; 
	right: 40%; 
} 
 
.add__button:after { 
	position: absolute; 
	display: block; 
	content: ''; 
	top: 50%; 
	transform: translate(-40%, -50%); 
	width: 2px; 
	background-color: #91a8c4; 
	height: 20px; 
	right: 40%; 
} 
 
.add__button:hover { 
	cursor: pointer; 
} 
 
.add__button:hover:before { 
	background-color: #3675bc; 
} 
 
.add__button:hover:after { 
	background-color: #3675bc; 
} 
 
.tasks { 
	margin-top: 20px; 
	padding: 0 20px; 
} 
 
.task { 
	position: relative; 
	border-bottom: 2px solid #f0f0f0; 
	padding: 10px 0; 
	display: -webkit-flex; 
	display: -moz-flex; 
	display: -ms-flex; 
	display: -o-flex; 
	display: flex; 
} 
 
.task__close { 
	width: 20px; 
	height: 20px; 
	border: 1px solid gray; 
	border-radius: 50%; 
	margin-right: 15.5px; 
	position: relative; 
} 
 
.task__close:before { 
	position: absolute; 
	display: block; 
	content: ''; 
	right: 6px; 
	top: 3px; 
	transform: rotate(45deg); 
	width: 5px; 
	height: 10px; 
	border-bottom: 1px solid rgba(128,128,128,0.8); 
	border-right: 1px solid rgba(128,128,128,0.8); 
	opacity: 0; 
	transition: .2s linear opacity; 
} 
 
.task__close:hover { 
	background-color: rgba(128,128,128,0.2); 
	cursor: pointer; 
} 
 
.task__close:hover:before { 
	opacity: 1; 
}

<!DOCTYPE html> 
<html lang="ru"> 
<head> 
	<meta charset="UTF-8"> 
	<meta name="viewport" content="width=device-width, initial-scale=1"> 
	<title>Document</title> 
</head> 
<body> 
 
	<section class="section"> 
		<div class="container"> 
			<div class="spheres"> 
				<div class="sphere health"> 
					<div class="svg__icon"> 
						<img src="https://image.flaticon.com/icons/svg/148/148838.svg" alt=""> 
					</div> 
					<div class="sphere__title"> 
						Здоровье 
					</div> 
				</div> 
				<div class="sphere intelligence"> 
					<div class="svg__icon"> 
						<img src="https://image.flaticon.com/icons/svg/1491/1491214.svg" alt=""> 
					</div> 
					<div class="sphere__title"> 
						Развитие 
					</div> 
				</div> 
				<div class="sphere sociality"> 
					<div class="svg__icon"> 
						<img src="https://image.flaticon.com/icons/svg/1078/1078011.svg" alt=""> 
					</div> 
					<div class="sphere__title"> 
						Отношения 
					</div> 
				</div> 
			</div>  <!-- .spheres --> 
		</div> <!-- .container --> 
 
		<div class="container fluid"> 
			<div class="add"> 
				<div class="add__title"> 
					Добавить задачу 
				</div> 
				<div class="add__input-wrapper"> 
					<input type="text" placeholder="Бег 1 км" class="add__input"> 
					<div class="add__button"></div> 
				</div> 
			</div> 
		</div> <!-- .container.fluid --> 
 
		<div class="container"> 
			<div class="tasks"> 
				<div class="task" data-id="0"> 
					<div class="task__close"></div> 
					Моя первая задача 
				</div> 
			</div> 
		</div> <!-- .container --> 
	 
	</section> 
 
</body> 
</html>