express.json([options])
This middleware is available in Express v4.16.0 onwards.
This is a built-in middleware function in Express. It parses incoming requests with JSON payloads and is based on body-parser.
Returns middleware that only parses JSON and only looks at requests where
the Content-Type header matches the type option. This parser accepts any
Unicode encoding of the body and supports automatic inflation of gzip and
deflate encodings.
A new body object containing the parsed data is populated on the request
object after the middleware (i.e. req.body), or an empty object ({}) if
there was no body to parse, the Content-Type was not matched, or an error
occurred.
As `req.body`'s shape is based on user-controlled input, all properties and
values in this object are untrusted and should be validated before trusting.
For example, `req.body.foo.toString()` may fail in multiple ways, for example
`foo` may not be there or may not be a string, and `toString` may not be a
function and instead a string or other user-input.
The following table describes the properties of the optional options object.
| Property | Description | Type | Default |
|---|---|---|---|
inflate | Enables or disables handling deflated (compressed) bodies; when disabled, deflated bodies are rejected. | Boolean | true |
limit | Controls the maximum request body size. If this is a number, then the value specifies the number of bytes; if it is a string, the value is passed to the bytes library for parsing. | Mixed | "100kb" |
reviver | The reviver option is passed directly to JSON.parse as the second argument. You can find more information on this argument in the MDN documentation about JSON.parse. | Function | null |
strict | Enables or disables only accepting arrays and objects; when disabled will accept anything JSON.parse accepts. | Boolean | true |
type | This is used to determine what media type the middleware will parse. This option can be a string, array of strings, or a function. If not a function, type option is passed directly to the type-is library and this can be an extension name (like json), a mime type (like application/json), or a mime type with a wildcard (like */* or */json). If a function, the type option is called as fn(req) and the request is parsed if it returns a truthy value. | Mixed | "application/json" |
verify | This option, if supplied, is called as verify(req, res, buf, encoding), where buf is a Buffer of the raw request body and encoding is the encoding of the request. The parsing can be aborted by throwing an error. | Function | undefined |