What does 'extended' mean in express 4.0?

I'm using express and also body-parser in my app.

app.use(bodyParser.urlencoded({ extended: false }));

But, What does 'extended' mean in express 4.0?

I found this

extended - parse extended syntax with the qs module.

However, I still can't understrand what it means.

If extended is false, you can not post "nested object"

person[name] = 'cw'

// Nested Object = { person: { name: cw } }

If extended is true, you can do whatever way that you like.

> When extended property is set to true, the URL-encoded data will > be parsed with the qs library.

On the contrary, > when extended property is set to false, the URL-encoded data will > instead be parsed with the querystring library.

---

The differences between parsing with qs library vs querystring library

• qs library allows you to create a nested object from your query string.

    var qs = require("qs")
    var result = qs.parse("person[name]=bobby&person[age]=3")
    console.log(result) // { person: { name: 'bobby', age: '3' } }
  

• query-string library does not support creating a nested object from your query string.

    var queryString = require("query-string")
    var result = queryString.parse("person[name]=bobby&person[age]=3")
    console.log(result) // { 'person[age]': '3', 'person[name]': 'bobby' }
  

• qs library will not filter out '?' from the query string.

    var qs = require("qs")
    var result = qs.parse("?a=b")
    console.log(result) // { '?a': 'b' }
  

• query-string library will filter out '?' from the query string.

    var queryString = require("query-string")
    var result = queryString.parse("?a=b")
    console.log(result) // { a: 'b' }
  

---

app.use(bodyParser.urlencoded({ extended: true })) // for parsing application/x-www-form-urlencoded

For more information, you may refer to Leonid Beschastny's answer, and npm compare qs vs query-string.

From the Body-Parser docs:

> A new body object containing the parsed data is populated on the request object after the middleware (i.e. req.body). This object will contain key-value pairs, where the value can be a string or array (when extended is false), or any type (when extended is true).

And

> The extended option allows to choose between parsing the URL-encoded data with the querystring library (when false) or the qs library (when true). The "extended" syntax allows for rich objects and arrays to be encoded into the URL-encoded format, allowing for a JSON-like experience with URL-encoded. For more information, please see the qs library.

Basically extended allows you to parse full objects.

Body Parser: Url Encoded