JSFiddle - React, Tailwind, and code Playground

HTML

<input type="file" id="fileinput" />
<select id='encoding'>
    <option value='windows-1251'> Windows-1251 </option>
    <option value='windows-1252'> Windows-1252 </option>
</select>

JavaScript

function readSingleFile(evt) {
    //Retrieve the first (and only!) File from the FileList object
    var f = evt.target.files[0]; 

    if (f) {
      var r = new FileReader();
      r.onload = function(e) { 
	      var contents = e.target.result;

        alert( "Got the file.n" 
              +"name: " + f.name + "\n"
              +"type: " + f.type + "\n"
              +"size: " + f.size + " bytesn"
              + "starts with: " + contents.substr(1, contents.indexOf("\n"))
        );  
      }
      var encoding = document.getElementById('encoding').value;
      r.readAsText(f,  encoding);
    } else { 
      alert("Failed to load file");
    }
  }

document.getElementById('fileinput').addEventListener('change', readSingleFile, false);