Javascript filter array -

why following function return undefined when executed? seems though filter function indeed return appropriate object i'm not seeing why can't passed callback function. i'm new js.

function getuserbyid(usersarr, userid, cb){   cb((usersarr.filter(function(el){     return el.id === userid;   })[0])); }  getuserbyid(users, '15a', function(user){   return 'the user id 15a has email of ' + user.email + ' name of ' + user.name + ' , address of ' + user.address; });   var users = [   {     id: '43d',     email: 'james@gmail.com',     name: 'james',     address: '16 n'   },   {     id: '15a',     email: 'carry@gmail.com',     name: 'carry',     address: '14 n'   },   {     id: '87t',     email: 'jeff@gmail.com',     name: 'jeff',     address: '23 n'   }, ]; 

if have array of objects, , 1 or more of objects have id property assigned '15a', filter should work.

here's example:

function getuserbyid(usersarr, userid, cb) {     cb(usersarr.filter(function (el) {         return el.id === userid;     })[0]); }  var users = [{     id: '15a',     name: 'bob',     email: 'bob@example.com',     address: '123 main street' }, {     id: 'zxv',     name: 'jim',     email: 'jim@example.com',     address: '234 main ave' }];  getuserbyid(users, '15a', function (user) {     document.getelementbyid('output').innerhtml = 'the user id 15a has email of ' + user.email + ' name of ' + user.name + ' , address of ' + user.address; }); 

jsfiddle: https://jsfiddle.net/0skhn9k9/2/

edit: make example work need return value of callback

function getuserbyid(usersarr, userid, cb){   return cb((usersarr.filter(function(el){     return el.id === userid;   })[0])); }  getuserbyid(users, '15a', function(user){   return 'the user id 15a has email of ' + user.email + ' name of ' + user.name + ' , address of ' + user.address; });   var users = [   {     id: '43d',     email: 'james@gmail.com',     name: 'james',     address: '16 n'   },   {     id: '15a',     email: 'carry@gmail.com',     name: 'carry',     address: '14 n'   },   {     id: '87t',     email: 'jeff@gmail.com',     name: 'jeff',     address: '23 n'   }, ];