index.js

var statuses = require('statuses');

var production = process.env.NODE_ENV === 'production';

var defaultLog = function (err) {
  console.error(err.stack);
};

module.exports = function (options) {
  var opts = options || {};
  var log = opts.log || defaultLog;

  return function apiErrorHandler(err, req, res, next) {
    var status = err.status || err.statusCode || 500;
    if (status < 400) status = 500;
    res.statusCode = status;

    var body = {
      status: status
    };

    // show the stacktrace when not in production
    // TODO: make this an option
    if (!production) body.stack = err.stack;

    // internal server errors
    if (status >= 500) {
      log(err, req, res);
      body.message = statuses[status];
      res.json(body);
      return;
    }

    // client errors
    body.message = err.message;

    if (err.code) body.code = err.code;
    if (err.name) body.name = err.name;
    if (err.type) body.type = err.type;

    res.json(body);
  }
}