App script code to create API from google sheets

gsscript

function doGet(req) {
  let spreadsheet = SpreadsheetApp.getActiveSpreadsheet();
  let personalDetails = spreadsheet.getSheetByName('personal-details'); //sheet name is personal-details
  let personalDetailsValues = personalDetails.getDataRange().getValues(); //reading the sheet data(2D array of sheet data)

  /*
    personalDetailsValues output
    [ [ 'First Name', 'Nikhil' ],
    [ 'Last Name', 'Bhatt' ],
    [ 'Email', '[email protected]' ] ]
  */

  let personalData = {}; // output hash
  for (let i = 0; i < personalDetailsValues.length; i++) {
    personalData[`${personalDetailsValues[i][0]}`] = personalDetailsValues[i][1];  //Getting the data in desired format
  }

  return ContentService
          .createTextOutput(JSON.stringify({personalData: personalData}))
          .setMimeType(ContentService.MimeType.json); //returning the data
}