how to convert json values in comma separated string using javascript

Answer 1

Simple:

var data = [{"name":"Marine Lines","location_id":3},{"name":"Ghatkopar","location_id":2}]
var result = data.map(function(val) {
  return val.location_id;
}).join(',');

console.log(result)

I assume you wanted a string, hence the .join(','), if you want an array simply remove that part.