my_parser.js

// Load the fs (filesystem) module.
var fs = require('fs');// 

// Read the contents of the file into memory.
fs.readFile('sample-log.txt', function (err, logData) {
  
// If an error occurred, throwing it will
  // display the exception and kill our app.
  if (err) throw err;
  
// logData is a Buffer, convert to string.
  var text = logData.toString();
  
var results = {};

// Break up the file into lines.
  var lines = text.split('\n');
  
lines.forEach(function(line) {
    var parts = line.split(' ');
    var letter = parts[1];
    var count = parseInt(parts[2]);
    
if(!results[letter]) {
      results[letter] = 0;
    }
    
results[letter] += parseInt(count);
  });
  
console.log(results);
  // { A: 8, B: 15, C: 4 }
});