Read a Spread sheet and display values with Google App Script

1. To open
   New >> More >> Google App Script

2. Rename
   

**A google script file will have this basic function ***

function doGetTest(e){
}

sligtly alter it like

function doGetTest(e){
if (e === undefined)e ={parameters:{}}// for running tests
}

3. To get the url variable passed use e.parameter;

eg:

var op = e.parameter.action;

4. Create google Spreadsheet Instance

   var SPREADSHEET_URL = 'https://docs.google.com/spreadsheets/d/sasasasasadqw323qsqw2333/edit?usp=sharing';
   var ss=SpreadsheetApp.openByUrl(SPREADSHEET_URL);
   var sheet = ss.getSheetByName("Sheet1");
   read_value(e,ss);

5. Write a function to read

   function read_value(request,ss){ 
   var output  = ContentService.createTextOutput(),
     data    = {};
   //Note : here sheet is sheet name , don't get confuse with other operation 
     var sheet="sheet1";
   //output.setContent('in read_value(request,ss)');return output;
   data.records = readData_(ss, sheet);
   
   var callback = request.parameters.callback;
   console.log(JSON.stringify(data));
   if (callback === undefined) {
   output.setContent(JSON.stringify(data));
   } else {
   output.setContent(callback + "(" + JSON.stringify(data) + ")");
   }
   output.setMimeType(ContentService.MimeType.JAVASCRIPT);
   
   return output;
   }
   function readData_(ss, sheetname, properties) {
   if (typeof properties == "undefined") {
   properties = getHeaderRow_(ss, sheetname);
   properties = properties.map(function(p) { return p.replace(/\s+/g, '_'); });
   }  
   var rows = getDataRows_(ss, sheetname),
     data = [];
   for (var r = 0, l = rows.length; r < l; r++) {
   var row     = rows[r],
       record  = {};
   for (var p in properties) {
     record[properties[p]] = row[p];
   }
   data.push(record);
   }
   return data;
   }
   function getDataRows_(ss, sheetname) {
   var sh = ss.getSheetByName(sheetname);
   return sh.getRange(2, 1, sh.getLastRow() - 1, sh.getLastColumn()).getValues();
   }
   function getHeaderRow_(ss, sheetname) {
   var sh = ss.getSheetByName(sheetname);
   return sh.getRange(1, 1, 1, sh.getLastColumn()).getValues()[0];  
   } 

6. Run