Why does one form file iteration work but the other throws % exception? (working with JSON parse in Google-apps-script)

Question

I was trying to use the method found here (see most up-voted answer): Google Apps Script Fastest way to find a row?

I currently use this while it does work I wanted to try the above linked method yet when I replace the below code

function AutoPopulate (evalue)
{
  
 //uses google drive file irretator reads in JSON file and parses it to a Javascript object that we can work with
  
  var iter = DriveApp.getFilesByName("units.json");
  // iterate through all the files named units.json
  while (iter.hasNext()) {
    // define a File object variable and set the Media Tyep
    var file = iter.next();
    var jsonFile = file.getBlob().getDataAsString();
    // log the contents of the file
    //Logger.log(jsonFile);
    
  }
  var UnitDatabase = JSON.parse(jsonFile);
  
//Logger.log(UnitDatabase);
//Logger.log(UnitDatabase[1027]);
return UnitDatabase[evalue];
}

WITH THIS CODE:

function AutoPopulate (evalue)
    {
    //this method did not work for me but should have according to stackflow answer linked above I am trying to understand why or how I can find out why it may have thrown an error
        var  jsonFile = DriveApp.getFilesByName("units.json").next(),
        UnitDatabase = UnitDatabase.getBlob().getDataAsString(); 
         return UnitDatabase[evalue];
}

I get an error in the excecution indicating that there is a % at postion 0 in the JSON, between the methods I dont alter the JSON file in anyway so I dont understand why does the top method work but the bottom one does not?

For further information the idea behind the code is that I have a list of Unit numbers and model numbers that are in a spreadsheet. I then convert this to a JSON file, this however is only done when a new unit is added to the fleet. As I learned one can parse a whole JSON file into a javascript object which makes working with the data set much faster. This javascript object is used so that when a user enters a UNIT# the MODEL# is auto populated based on the JSON file.

I cannot share the JSON file as it contains client information.

Answer 1

Your code does not work for two reasons:

1. You have a typo in the line UnitDatabase = UnitDatabase.getBlob()... - it should be UnitDatabase = jsonFile.getBlob()...
2. If you want to retrieve a nested object from a json file - you need to parse the JSOn - otherwise it is considered a string and you can not access the nested structure

Modified working code:

function AutoPopulate2 (evalue)
{
  var  jsonFile = DriveApp.getFilesByName("units.json").next();
  var UnitDatabase = JSON.parse(jsonFile.getBlob().getDataAsString()); 
  return UnitDatabase[evalue];
}

Mind that this code will only work if you have a "units.json" file on your drive and if evalue is a valid 1st-level nested object of this json.