Why forEach method doesn't work on HTMLCollection-CodePudding

I was learning about DOM manipulation and have an HTML document.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <h1 >
        Title
    </h1>
    <h2 >
        Here is the list of all the programming languages:
    </h2>
    <ul>
        <li>JavaScript</li>
        <li>Python</li>
        <li>Go</li>
    </ul>
    <script>
        const test = document.getElementsByClassName('test');
        test.forEach(item => {
            console.log(item);
        });
    </script>
</body>
</html>

I have tried accessing the html elements using forEach method but it gives error saying that test.forEach is not a function.

CodePudding user response：

Because HTMLCollections aren't Arrays. (For one, as the docs say, a HTMLCollection is live and can change when the document changes; an array can't.)

You can use Array.from(test) or [...test] spreading to make an Array of something that has a .length and supports item access (which HTMLCollection does).

IOW,

<script>
const test = document.getElementsByClassName('test');
[...test].forEach(item => {
  console.log(item);
});
</script>

CodePudding user response：

Rather than using getElementsByClassName, try querySelectorAll

const test = document.querySelectorAll('.test');
test.forEach(item => {
    console.log(item);
});

Simple and work like a charm.

CodePudding user response：

HTMLCollection is not an Array but an object. So you can use for loop or you can convert it into an array by doing [...test].