JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="output"></pre>

JavaScript

var values = [{
"name" : "fhj",
"age" : "23",
"gender" : "female",
"sec" : "b",
"username" : "9886666",
"language" : "HINDI",
"method" : "method2",
"timeSlot" : {
    "id" : 2,
    "fromTime" : 12,
    "toTime" : 15
}
}];

if(!values.length)
   console.log("ERROR !!!!");
else
{ 
   var i=1;
   str='[';
   values.forEach(function(user){
     if(i==values.length)
         str=str+'{ "name" : "' + user.username + '","age" : "'+ user.age +'","gender":"'+user.gender+'","sec":"'+user.sec+'","username":"'+user.username+'","language":"'+user.language+'","method":"'+user.method+'","Timeslot":"'+ JSON.stringify(user.timeSlot) +'"}';
     else{
       str = str + '{ "name" : "' + user.username + '","age" : "'+ user.age +'","gender":"'+user.gender+'","sec":"'+user.sec+'","username":"'+user.username+'","language":"'+user.language+'","method":"'+user.method+'","Timeslot":"'+ JSON.stringify(user.timeSlot)+'"},' +'\n';
       i++;
     }
   });
   str = str.trim();
   str = str + ']';

   document.getElementById('output').innerHTML = str;
  }
   
   
   
   
   
   document.write