gistfile1.js

var fs = require('fs');
fs.readFile('./source.txt', function (err, content) {
  var array = content.toString().split('\n');
  var container = {};
  array.forEach(function (num) {
    container[num] = 1;
  });
  var lookingFor = process.argv.pop();
  console.log('looking for ' + lookingFor);
  for (var i in container) {
    if (container[lookingFor - i] === 1) {
      console.log('yes');
      process.exit(0);
    }
  }
  console.log('no');
});