Insert, Update and Delete with Google App Script

function insert_value(request,sheet){ 
   var id = request.parameter.id;
  var country = request.parameter.name;  
  var flag=1;
  var lr= sheet.getLastRow();
  for(var i=1;i<=lr;i++){
    var id1 = sheet.getRange(i, 2).getValue();
    if(id1==id){
      flag=0;
  var result="Id already exist..";
    } }
  //add new row with recieved parameter from client
  if(flag==1){
  var d = new Date();
    var currentTime = d.toLocaleString();
  var rowData = sheet.appendRow([currentTime,id,country]);  
  var result="Insertion successful";
  }
     result = JSON.stringify({
    "result": result
  });      
  return ContentService
  .createTextOutput(request.parameter.callback + "(" + result + ")")
  .setMimeType(ContentService.MimeType.JAVASCRIPT);   
  }

//update function

function update_value(request,sheet){

var output  = ContentService.createTextOutput();
   var id = request.parameter.id;
  var flag=0;
  var country = request.parameter.name;
  var lr= sheet.getLastRow();
  for(var i=1;i<=lr;i++){
    var rid = sheet.getRange(i, 2).getValue();
    if(rid==id){
      sheet.getRange(i,3).setValue(country);
      var result="value updated successfully";
      flag=1;
    }
}
  if(flag==0)
    var result="id not found";

   result = JSON.stringify({
    "result": result
  });  

  return ContentService
  .createTextOutput(request.parameter.callback + "(" + result + ")")
  .setMimeType(ContentService.MimeType.JAVASCRIPT);   

}

function delete_value(request,sheet){

  var output  = ContentService.createTextOutput();
   var id = request.parameter.id;
  var country = request.parameter.name;
  var flag=0;

  var lr= sheet.getLastRow();
  for(var i=1;i<=lr;i++){
    var rid = sheet.getRange(i, 2).getValue();
    if(rid==id){
      sheet.deleteRow(i);
      var result="value deleted successfully";
      flag=1;
    }

  }

  if(flag==0)
    var result="id not found";

   result = JSON.stringify({
    "result": result
  });  

  return ContentService
  .createTextOutput(request.parameter.callback + "(" + result + ")")
  .setMimeType(ContentService.MimeType.JAVASCRIPT);   

}