Javascript 使用此变量获取索引值

Question

当我单击 li 链接时，我想使用此变量获取索引值。我怎样才能实现它？

let liList = document.getElementsByTagName("li");
for (let i = 0; i < liList.length; i++) {
    liList[i].onclick = function () {
       alert(liList.indexOf.call(this));        //I want to use this to get i value
    };
 }

<ul>
    <li>11</li>
    <li>22</li>
    <li>33</li>
</ul>

Answer 1

如果你想获得点击值的索引，则不需要执行 indexOf，你的循环中有索引 i变量:

let liList = document.getElementsByTagName("li");
for (let i = 0; i < liList.length; i++) {
    liList[i].onclick = function () {
       console.log(i);
    };
 }

<ul>
    <li>11</li>
    <li>22</li>
    <li>33</li>
</ul>

如果你真的想做 indexOf()你应该改变那个 HTMLCollection首先从 getElementsByTagName() 返回到数组:

let liList = document.getElementsByTagName("li");
for (let i = 0; i < liList.length; i++) {
    liList[i].onclick = function () {
        let arr = Array.prototype.slice.call( liList, 0 ); // transform in array
        console.log(arr.indexOf(this));
    };
 }

<ul>
    <li>11</li>
    <li>22</li>
    <li>33</li>
</ul>