js还能使用数组标记来获取有id或name属性的元素吗？

我在学习js的基础知识的时候，按照书上的例子打以下代码

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Example</title>
        <style>
            pre{border:medium double black;}
        </style>
    </head>
    <body>
        <pre id="results"></pre>
        <img src="img/lemon.png" alt="lemon" id="lemon">
        <p>
            There are lots of different kinds of fruit - there are over 500
            varieties of banana alone.By the time we add the
            countless types of apples,oranges,and other well-known fruit,we are faced
            with thousands of choices.
        </p>
        <img id="apple" src="img/apple.png" alt="apple">
        <p>
            One of the most interesting aspects of fruit is the
            variety avaliable in each country.I live near London,in an area which is
            known for its apples.
        </p>
        <img src="img/banana-small.png" id="banana" alt="small banana" >
        <script>
            var resultsElement = document.getElementById("results");
            var elems = document["apple"];
            if (elems.namedItem){
                for (var i = 0; i < elems.length; i++){
                    resultsElement.innerHTML += "Image Element: "+elems[i].id + "\n";
                }
            } else{
                resultsElement.innerHTML += "Src for element is: "+elems.src + "\n";
            }
        </script>
    </body>
</html>

但是一直没有结果，浏览器显示elems是undefined，是

var elems = document["apple"];

这句话出了问题吗？

下面是书上关于这种方法的解释，但是我不知道为啥我没有成功获得id为apple的元素，而用其他方法，如document.images.namedItem("apple")等方法是可以获取的

图片说明

https://blog.csdn.net/weixin_30897079/article/details/96083760

你是想干啥啊获取id为 apple的节点吗
那样的话直接 var a= doucment.getElementById("apple");
就行啦