Insert javaScript function inside FreeMarker template

Question

I have a problem introducing a js function inside ftl.

I have a javaScript function which converts a value from bytes to kilobytes, on the other side I need to call that function in ftl. I am using script tag, but when I want to assign the calculated value and print it, I get nothing.

This is my js function:

function formatBytes(bytes, decimals = 0) {
    if (bytes === 0) return "0 Bytes";

    const k = 1024;
    const dm = decimals < 0 ? 0 : decimals;
    const sizes = ["Bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"];

    const i = Math.floor(Math.log(bytes) / Math.log(k));
    return parseFloat((bytes / Math.pow(k, i)).toFixed(dm)) + " " + sizes[i];
}

And this is the way how I tried to call it inside ftl:

<span class="inner">
                           
  <span class="label">Size:</span>
  <span class="value">
     <#assign size = node.size>
     <#assign sizeInBytes = size>
        <script>
        <#assign result = "" >
         result = formatBytes(${sizeInBytes?replace(",", "", "r")});
        </script>
       ${result}
                              
</span>

I tried also this:

<span class="value">
    <#assign size = node.size>
    <#assign sizeInBytes = size>
     <script>
     <#assign result = formatBytes('${sizeInBytes?replace(",", "", "r")}') >
     </script>
    ${result}
</span>