Consider the following code
function readSingleFile(evt) {
//Retrieve the first (and only!) File from the FileList object
var myFile = evt.target.file
That's not how you get the result of a FileReader
. Modify your code to this:
function readSingleFile(evt) {
//Retrieve the first (and only!) File from the FileList object
var myFile = evt.target.files[0];
var reader = new FileReader();
reader.readAsText(myFile);
reader.onload=function(){alert(reader.result)}
}