Transferring data from one collection to another

Try:

exportfunction btnStart_click(event){
    copyRowsCount()
}

That way you were not invoking the function, just its content.

Try adding console.log() with the variables you want to check if something returned, for example:

if (allItems.length > 0) {
    while(query.hasNext()) {
        query = awaitquery.next()
        allItems = [...allItems, ...query.items]
    }
} // This is going to retrieve all the items from the Source collection.
console.log(allItems) // Check if something returned.

Also, you need to rename the collections you want to copy from and to, in my example I used ‘Source’ and ‘Destination’ because I was not sure what was the name of yours.