1、JavaScript创建块级作用域
（1）方法一：ES6
（2）方法二：闭包
2、示例
<!DOCTYPE html>
<html lang="zh">
<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>JavaScript创建块级作用域</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script>
var li = document.getElementsByTagName('li');
//方法一：ES6创建块级作用域
function closure() {
for(let i = 0, len = li.length; i < len; i++) {
li[i].onclick = function() {
console.log(i)
}
}
}
//方法二：使用闭包创建块级作用域
function closure2() {
for(var i = 0, len = li.length; i < len; i++) {
li[i].onclick = (function(i) {
return function() {
console.log(i)
}
})(i);
}
}
closure();
closure2();
</script>
</body>
</html>