Is it possible to await a function that doesn't return anything

I have a for loop that fetches code from another file and appends it to my website using the insertAdjacentHTML() method. After that it modifies the innerHTML of the freshly added piece of code. My current solution looks something like this:

for (let i = 0; i < 3; i++) {
    fetch("myFile.html")
    .then((obj) => obj.text())
    .then((text) => {
        document.getElementById("addContentHere").insertAdjacentHTML("beforeend", text);
        document.getElementsByClassName("elementInAddedContent")[i].innerHTML = "Modified content";
    });
}

In my website I have the following code:

<div id="addContentHere"></div>

And the HTML that I'm fetching is something like this:

<div class="addedElement">
    <div class="elementInAddedContent"></div>
</div>

So the end result in my website should look like this:

<div id="addContentHere">
    <div class="addedElement">
        <div class="elementInAddedContent">Modified content</div>
    </div>
    <div class="addedElement">
        <div class="elementInAddedContent">Modified content</div>
    </div>
    <div class="addedElement">
        <div class="elementInAddedContent">Modified content</div>
    </div>
</div>

Of course all added elements are going to have different content, but for example purpouses I'm keeping it simple. The problem is that the computer reaches the document.getElementsByClassName("elementInAddedContent")[i].innerHTML = "Modified content"; before the element has been added and so I get the Uncaught (in promise) TypeError: Cannot set properties of undefined (setting 'innerHTML') error. Can I somehow use await on code that doesn't itself return anything? So something like this:

for (let i = 0; i < 3; i++) {
    fetch("myFile.html")
    .then((obj) => obj.text())
    .then((text) => {
        await document.getElementById("addContentHere").insertAdjacentHTML("beforeend", text);
        document.getElementsByClassName("elementInAddedContent")[i].innerHTML = "Modified content";
    });
}

Your loop is trying as fast as possible to read a file, update the DOM and read again and update again. There is no control over what is happening since Fetch is async. I still do not understand why you had a loop around getting ONE file..

Perhaps you meant to do this?

I give the DOM 100 ms to be updated

<!-- language: lang-js -->

fetch("myFile.html")
  .then((obj) => obj.text())
  .then((text) => {
    document.getElementById("addContentHere").insertAdjacentHTML("beforeend", text);
    setTimeout(() => document.querySelectorAll(".elementInAddedContent").forEach(el => el.textContent = "Modified content"), 100);
  });

<!-- end snippet -->