Javascript. Почему data = null?

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<link rel="stylesheet" href="css/style.css">
</head>
<body>
<div class="tabs">
<ul>
<li data="1">1</li>
<li data="2">2</li>
<li data="3">3</li>
</ul>
</div>
<div class="text" data="1">text1</div>
<div class="text" data="2">text2</div>
<div class="text" data="3">text3</div>
<script src="script.js"></script>
</body>
</html>
let tabs = document.querySelectorAll(".tabs");
for (let i = 0; i < tabs.length; i++){
tabs[i].onclick = function(){
let data = this.getAttribute("data");
console.log(data);
};
}
04 мая 2020 в 21:10