How to Implement Restify server.put? - node.js

Question

Hi there I'm starting to Develop Restful API using Restify but I'm having problems developing [PUT].
My idea is to get the params and change it using the new params. But this code does not seem to work. Please help me out :D
server.put('/user/:_id', function (req, res, next) {
var user = {};
user._id = req.params._id;
console.log('_id === '+user);
var changes = req.params;
delete changes._id;
// delete changes._id;
for(var x in changes) {
user[x] = changes[x];
console.log('user[x] ='+user[x]);
}
db.Student.update(req.params._id, user,{multi:true,upsert:true}, function(err,data){
res.writeHead(200, {'Content-Type': 'application/json; charset=utf-8'});
res.end(JSON.stringify(user));
return next();
});
});
here is the putclient
var restify = require('restify');
var server = require('./app');
var client = restify.createJsonClient({
url: 'http://localhost:3000'
});
var testUser = {
$set:
{
"name" : "procopio magalpok",
"yearLevel" : "IX"
}
};
testUser._id = "561de16f885fb2f40d23ece",
client.put('/user/'+testUser._id, testUser , function (err, req, res, status) {
if (err) {
console.log("An error ocurred >>>>>>");
console.log(err);
} else {
console.log('id : '+testUser._id);
console.log('User updated >>>>>>>');
console.log(status);
}
});