Meaning of argument in express.json({ extended: false})

Question

I'm working with express to set up an API, and I came across this line of code: app.use(express.json( { extended: false } ));

I've seen the documentation from express, but I didn't find this method, is the documentation lacking or am I missing something?

Answer 1

Answers come from looking at the actual Express and body-parser code...

If you go look at the Express code for the express.json() method here, you can see that it is a direct pass-through of the .json() method from the body-parser module.

 // from express.js
 exports.json = bodyParser.json;

So, if you then go look at the body-parser doc, there is nothing there for the extended option for the body-parser.json() middleware.

As you have discovered, the extended option is documented for the body-parser.urlencoded() middleware. But, since that is different than the .json() middleware method, it appears that this code is mistaken to be using the extended option with the .json() middleware.

If you go look at the code for the body-parser.json() middleware, you will find no references at all to the extended option in the code.

So, it appears to be an option that is mistakenly passed in the code you show and is subsequently ignored by the express/body-parser json middleware.