Export Google Spreadsheet as JSON

export.gs

function exportJSON() {
  var sheets = SpreadsheetApp.getActiveSpreadsheet().getSheets();
  var result = sheets.reduce(function(result, sheet) {
    var id = sheet.getName().toLowerCase();
    var data = sheet.getDataRange();    
    var values = data.getValues();
    
    result[id] = values.map(function(row) {
      return row.map(function(column) {
        return Math.round(column) || column;
      }).filter(Boolean);
    }).filter(function(row) {
      return !!row[0];
    });

    return result;
  }, {});
  
  var app = UiApp.createApplication().setTitle('Exported JSON');
  var textArea = app.createTextArea().setWidth('100%').setHeight('400px').setText(JSON.stringify(result));
  app.add(textArea);

  SpreadsheetApp.getActiveSpreadsheet().show(app);
};