I’ve got the bytes string converting to a number, so that’s all good. Now the next question, @Bugsounet how do I use your function within the JSON.parse function?

                var payload = JSON.parse(payload, function (key, value) {
                    if ( key === 'down_rate' ) {
                    var num = Number(value);
                    return (num/(1024*1024)).toFixed(2);
                    }

Just to add, I had tried the following and receive a this.convert is not a function

                    var downrate = this.convert(value,0);
                    return downrate;

  convert: function(octet,FixTo) {
    octet = Math.abs(parseInt(octet, 10));
    var def = [[1, 'b'], [1024, 'Kb'], [1024*1024, 'Mb'], [1024*1024*1024, 'Gb'], [1024*1024*1024*1024, 'Tb']];
    for (var i=0; i < def.length; i++) {
      if (octet < def[i][0]) return (octet/def[i-1][0]).toFixed(FixTo)+def[i-1][1];
    }
  },

Syntax:
octet: octets to transform
FixTo: precision of the result

Fixto precision sample: if you set it to 2 result is : X.XX, if you set it to 3result is X.XXX

Of course, Unit is automaticaly set ! b /Kb/Mb/Mb/Tb
That’s to you to adapt if you want to use it ;)

parse converts to number if possible
then math works.

number/(1024*1024)
is parts of megabyte

                var payload = JSON.parse(payload, function (key, value) {
                    if ( key === 'down_rate' ) {
                    return (value / 1024 / 1024).toFixed(2);
                    }
                    else if ( key === 'up_rate' ) {
                    return (value / 1024 / 1024).toFixed(2);
                    }
                    else {
                    return value;
                    }
                });

I’m sure there is a proper way of doing this, but for my needs this is now working as needed.

basically t.data[i].down_rate / 1024 for kilobytes

what math would you use to convert that to

kilobytes ( 1024)
or
megabytes (1024"1024)

bytes/second