example.js

var parseCSV = require("./parse-csv.js");

// Call the function, pass a callback as the second arg
parseCSV("data.csv",function(err,rows){

  // Did something go wrong?
  if (err) {
    throw new Error(err);
  }
 
  //rows is an array of rows
  console.log(rows);

});

parse-csv.js

// Make an existing module do the hard part
var fs = require("fs"),
    csv = require("dsv")(",");
 
// Export a function that expects two args: the filename and a callback
module.exports = function(filename,callback) {
 
  // Read the file, asynchronously
  fs.readFile(filename,"utf8",function(err,rawText){
 
    // If something went wrong, call the callback with an error
    if (err) {
      return callback(err,null);
    }
 
    // Call the callback with the parsed data
    return callback(err,csv.parse(rawText));
 
  });
 
};