My ‘AutoType’ function to type words automatically DOESN’T WORK

Details

Its a simple code. It gets the words in all .auto-type elements as input, then
type them automatically.

Here’s the CodePen : https://codepen.io/akolad/pen/zYPoEWd

Codes

  • javascript
    window.onload = () => {
    let elements = document.getElementsByClassName("auto-type");
    for (element of elements) {
        const text = element.innerHTML.toString();
        let charIndex = 0;
        const typing = () => {
            element.innerHTML += text.charAt(charIndex);
            if (charIndex < text.length) {
                setTimeout(typing, 100);
                charIndex++;
            }
        };
    }
};
  • html (body)
    <body>
    <span class="auto-type code">hello!</span>
    <br />
    <span class="auto-type code">some text</span>
    <br />
    <div class="auto-type">some other text</div>
    <span class="auto-type code">here is a better text</span>

    <!-- js file: -->
    <script type="text/javascript" src="AutoType.js"></script>
</body>

Problem

actually, js codes doesn’t work. and console is empty(no errors).
where’s the problem?