why is that when i am trying to set the value of a key inside an object ,it is also modifying the data originaly from where the value is being fetched

Question

for (let i = 0; i < diffOfDays; i++) {
  let taskgroup = config.TG["TG" + (i + 1)]
  taskgroup = taskgroup.split(',')

  for (let j = 0; j < taskgroup.length; j++) {
    taskgroup[j] = taskgroup[j].trim()
    taskId = "t" + x

    taskOb[`${taskId}`] = config['Tasks'][taskgroup[j]]

    taskOb[`${taskId}`]['d'] = i + 1

    x++
  }
}

When I am setting data in taskOb, the value I want to set it to is config['Tasks'][taskgroup[j]]. After that when I add the 'd' key in taskOb[taskId], the 'd' key also gets added to config['Tasks'][taskgroup[j]]. The config object is a big object having several keys.