Callback with mutable error message.

gistfile1.js

var fs = require('fs');

var errorHandler = function(err, result) {
  return function(customMessage) {
      if (err) return err;
      else {
        // Call some other sync function but with my message
        console.log(customMessage);
        handleResult(result);
      }  
  }

};


fs.readFile('readme.md', 'utf-8', errorHandler()('hahahhah this does not work as this requires extra wrapper'));
fs.readFile('other.md', 'utf-8', errorHandler()('Actually the main point is to reuse code'));

I think you want something more like

function fileReadHandler(message) {
  return function(err, data) {
    if(err) throw err
    else {
      console.log(message)
      handleData(data)
    }
  }
}

fs.readFile('file.foo', 'utf-8', fileReadHandler('custom message'))