gistfile1.js

var util = require('util');
var _ = require('underscore');
 
httpError('NotFound', 'Not Found', 404);
httpError('Server', 'There was an error', 500);
httpError('Unauthorized', 'You must log in to access this', 401);
httpError('Forbidden', 'You do not have permission to access this', 403);
httpError('BadRequest', 'There was an error with your input', 400);
 
function httpError(name, default_msg, status_code) {
  var fn = function(err, opts) {
    if (util.isError(err)) {
      _.extend(this, err);
      if (!this.message) this.message = default_msg;      
    } else if (_.isString(err)) {
      this.message = err;
    } else {
      this.message = default_msg;
    }
 
    this.status_code = status_code;
    
    if (!util.isError(err) && !_.isString(err)) opts = err;
    if (opts) this.layout = opts.layout;
 
    Error.captureStackTrace(this, arguments.callee);
  }
  
  util.inherits(fn, Error);
  fn.prototype.name = name;
  
  global[name + 'Error'] = fn;
}