Why does CloudKit JS "sortBy" return a different order on Safari?

Question

I'm trying to mirror a high scores leader board from my app on a webpage. Following an old raywenderlich tutorial I am using CloudKit JS and Knockout to accomplish this. Naturally, I want to sort by scores from highest to lowest.

The example code in the tutorial uses:

var query = { recordType: 'CD_FinalScore', sortBy: [{ fieldName: 'CD_score'}] };

(Of course, I am plugging in my recordType and fieldName for the example ones.) This did not give me the results I wanted, so I added a sort method on the records fetched by the query:

self.items(records.sort(function(a, b){return b - a}));

This gives me the results I want on Firefox but not on Safari (where the order is the inverse). My gut tells me that I need to focus on the query signature. Can someone tell me what I've done wrong or incompletely? Thanks! For reference, the complete Knockout view model code is here:

function LeaderboardViewModel() {
    var self = this;
    var container = CloudKit.getDefaultContainer();
    var publicDB = container.publicCloudDatabase;
    self.items = ko.observableArray();
    self.fields = ko.observable('');
    self.fields.CD_score = ko.observable('');
    self.fields.CD_userName = ko.observable('');
    self.fields.CD_submitDate = ko.observable('');

    self.fetchRecords = function() {
      var query = { recordType: 'CD_FinalScore', sortBy: { fieldName: 'CD_score' } };
     
      // Execute the query.
      return publicDB.performQuery(query).then(function(response) {
        if(response.hasErrors) {
          console.error("response errors: " + response.errors[0]);
          return;
        }
       var records = response.records;
        var numberOfRecords = records.length;
        if (numberOfRecords === 0) {
          console.error('No matching items');
          return;
        }
        //self.items(records); // this is per the original, tutorial
        self.items(records.sort(function(a, b){return b - a}));
      });
    };

      container.setUpAuth().then(function(userInfo) {
      console.log("setUpAuth");
      self.fetchRecords(); 
      });
  }
  ko.applyBindings(new LeaderboardViewModel()); 

});

Answer 1

Following the advice from user3297291 (particularly in the link provided), I changed the sort to the following:

self.items(records.sort(function(a, b) {
          return parseFloat(b.fields.CD_score.value) - parseFloat(a.fields.CD_score.value);
        }));

And this appears to be working in both browsers (Firefox and Safari).