How to pass a lot of data sequentially through Socket.io?

Question

JavaScript

From the server side, an SQL query is made, resulting in a lot of data. 15k lines on average. This chunk of strings is then sorted by date, where date is the array key, and the value of each is a list of objects for that date. Those. something like:

points[row.time_update] = [ {val1: 1, val2: 123, val6:321}, {val1: 21, val2: 777, val6:2} ... ]

Those. The solution to the problem through limit \ offset does not work for me. And what is the problem:
the code hangs on the client side (the code is exemplary everywhere, but reflects the essence):

socket.on('update_recv', function(data) { 
  console.log(data);
});

on the server is this:

socket.on('update', function(data){ 
   knex(sql .... ).then(function(rows){
      // обрабатываем строки, собираем массив points требуемого формата. 
      
     var keys = Object.keys(points); // необходимость выдавать порционно по датам
     for( var k in keys )
     {
       // вот тут начинается неведомая мне магия. Если брякнуть после socket.emit
       // то данные прилетают. т.е. 1 раз. в ином случае цикл идет, но на фронт
       // ничего не приходит. 
       socket.emit('update_recv', {result: JSON.stringify(points[keys[k]]) })
       sleep.sleep(3); // нужна задержка, пока грубая
      }
   });
});

How can I sequentially, with time intervals, pass a bunch of lines to the front? Transferring in one "package", followed by processing there, is considered not very reasonable, plus it is not transmitted anyway.

Answer 1

It's hard to see from a mobile, but the data is drawn to economical packaging