变量声明赋值与立即执行函数

Question

<script>
        var btn1 = document.getElementById('btns');
        var ul = document.querySelector(".list");
        var li = document.getElementsByTagName('li');
        var btn2 = ul.getElementsByTagName("button");

        btn1.onclick = function () {
            ul.innerHTML = ''
        }
        for (var i = 0; i < btn2.length; i++) {
            var b = btn2[i]     // 这里加上;标识符就会正常运行,不加的话就报错     Uncaught TypeError: btn2[i] is not a function
                (function (b) {
                    b.onclick = function () {
                        b.parentNode.remove()
                    }
                })(b);
        }


    </script>