选项卡功能！本地好用！上传之后报错了！

       let obtn = document.getElementsByTagName("li");
        let oElec = document.getElementsByClassName("elec");

        let i = 0;

        for (i = 0; i < obtn.length; i++) {
            obtn[i].index = i;//记录索引值
            obtn[i].onclick = function () {
                for (let j = 0; j < obtn.length; j++) {
                    obtn[j].className = "";
                    oElec[j].style.display = 'none';
                }
                this.className = "active";
                oElec[this.index].style.display = "block";
            };
        }

118.php:269 Uncaught TypeError: Cannot read properties of undefined (reading 'style')
at obtn..onclick (118.php:269:30)

解决了，这个选择器获取到了不应该获取的 li
let obtn = document.getElementsByTagName("li");

无法读取未定义的属性(读取'style') ，obtn 和 oElec 确定有值。类型是数组吗

oElec[j] 或者 oElec[this.index]没有值导致的