Difference between res.send and res.json in Express.js
The methods are identical when an object or array is passed, but res.json()
will also convert non-objects, such as null
and undefined
, which are not valid JSON.
The method also uses the json replacer
and json spaces
application settings, so you can format JSON with more options. Those options are set like so:
app.set('json spaces', 2);app.set('json replacer', replacer);
And passed to a JSON.stringify()
like so:
JSON.stringify(value, replacer, spacing);// value: object to format// replacer: rules for transforming properties encountered during stringifying// spacing: the number of spaces for indentation
This is the code in the res.json()
method that the send method doesn't have:
var app = this.app;var replacer = app.get('json replacer');var spaces = app.get('json spaces');var body = JSON.stringify(obj, replacer, spaces);
The method ends up as a res.send()
in the end:
this.charset = this.charset || 'utf-8';this.get('Content-Type') || this.set('Content-Type', 'application/json');return this.send(body);
res.json
eventually calls res.send
, but before that it:
- respects the
json spaces
andjson replacer
app settings - ensures the response will have utf8 charset and application/json content-type
Looking in the headers sent...
res.send uses content-type:text/html
res.json uses content-type:application/json
edit: send actually changes what is sent based on what it's given, so strings are sent as text/html, but it you pass it an object it emits application/json.