Express Error: No default engine was specified and no extension was provided

http://stackoverflow.com/questions/23595282/error-no-default-engine-was-specified-and-no-extension-was-provided

Error: No default engine was specified and no extension was provided. 
at new View (...\node_modules\express\lib\view.js:41:42) 
at Function.app.render (...\node_modules\express\lib\application.js:484:12) 
at ServerResponse.res.render (...\node_modules\express\lib\response.js:783:7) 
at Layer.handle (...\app.js:123:7) 
at trim_prefix (...\node_modules\express\lib\router\index.js:225:17) 
at c (...\node_modules\express\lib\router\index.js:198:9) 
at Function.proto.process_params (...\node_modules\express\lib\router\index.js:253:12) 
at next (...\node_modules\express\lib\router\index.js:189:19) 
at next (...\node_modules\express\lib\router\index.js:202:7) 
at next (...\node_modules\express\lib\router\index.js:166:38)

Answer: 

The res.render stuff will throw an error, if you're not using a view engine.

If you just want to serve json replace the res.render('error', { error: err }); lines in your code with:

res.json({ error: err })

PS: People usually also have message in the returned object:

res.status(err.status || 500);
res.json({
  message: err.message,
  error: err
});