I've seen a few similar questions asked, but couldn't get them to work with my code so just wanted to see if I could get some additional help - my code below:

const upload(input, file){

  var fileUploadedCorrectly = true

  file.onload = (e) =>{
   if(code checking if extension is .csv){
      fileUploadedCorrectly = true;
    } else {
      fileUploadedCorrectly = false;
    }
   }
}

function retrieve(in){
  const file = in.files[0];

  if (fileUploadedCorrectly){
   code to continue upload
  } else {
   code to display error message
  }
}

I'm having trouble with accessing the value of fileUploadedCorrectly in the retrieve() function. Any help would be much appreciated - thank you very much.