ECMAScript 6 features unavailable - Custom input activity

Hi, guys.

Currently when executing the HTML file through custom input activity (CIU), I’m getting messages that indicate that some features from JS may not be available .
For example:

“Error: ‘Fetch’ is not defined.”

Now, if the problem arises from support issues (because IE11 doesn’t support FETCH), how should I approach this efficiently? Perhaps through Polyfill. I’m not sure.

This is the JS code:

function LeerDatos() {
    // Qué hacer en caso de error
    if (!res.ok) throw new Error("No se pudo leer la base de datos.");
    return res.arrayBuffer();
    // Leemos los datos
    const rawData = new Uint8Array(data);
    const workbook =,{type: "array"})
     // Convertimos de Excel a JSON

    // Obtenemos el nombre la primera hoja del libro 
    const firstSheetName = workbook.SheetNames[0];
    // Leemos la primera hoja
    const worksheet = workbook.Sheets[firstSheetName];
    // Conversión
    const jsonData = XLSX.utils.sheet_to_json(worksheet, {raw: true});


I’ve also got this meta tag in the HTML:

<meta http-equiv="X-UA-Compatible" content="IE=11" />

I’ve tried by changing it to “IE=edge” and “Chrome=1” but it’s not working.
<meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">

I would assume that you also tried above, right?

Hi, yes I did. That’s why I made this question. I don’t know what else to do. :confused:

then I would suggest to go ahead with a Polyfill RnD or to rethink if you have an alternate to achieve what you want to achieve. Currently we don’t know the goal of your intententions.