javascript - jQuery ajax call getting error response with status of 200 -

i sent jquery ajax request express-powered node.js server, processed , responded. however, response triggers ajax error callback instead of success callback (despite status code being "200"). not expecting. ;o) here code:

client.js:

$.ajax( {     url: "/httpupload",     type: "post",     processdata: false,     contenttype: false,     datatype : "json",     data: formdata,     success: function() {         // stuff     },     error: function( error ) {         console.error( "httpupload failed: " + error.responsetext );     } } ); 

server.js:

var express = require( "express" ); var app = express(); var server = require( "http" ).server( app ); var multipart = require('connect-multiparty');  app.use( express.static( "public" ) ); app.use( multipart() );  app.post( "/httpupload", function( req, res ) {     console.log( "received post request");     res.send( "done!" ); } 

the error object in ajax error callback looks this:

{readystate: 4, responsetext: "done!", status: 200, statustext: "ok"} 

any idea why it's triggering error callback?

oh, silly me. it's datatype had on ajax call. wasn't returning json, errored out. worked when removed that.