Async/Sync JS example

js-async.js

var fs = require('fs')

// So, callbacks.  When readFile is complete, the callback is 'called'
// And we get our console.log without blocking whatever might be next.
var file = fs.readFile('./example', 'utf-8', function(err, contents){
  if (err)
    console.log('You iz dumb');
  else
    console.log(file);
});

sync.js

var fs = require('fs')

// Sequential parsing of commands. Depending on the size of file
// This could keep the program locked up for quite a while.
var file = fs.readFileSync('./example', 'utf-8')
console.log(file);

Took me a very long time to understand callbacks. This is what made it clear to me.