DHT22 problem

Let me restate the problem.
I pulled the DHT22.js module and inserted a console.log for illustration.
Here is where the console.log was inserted

    delete ht.watch;
    var cks = 

        parseInt(d.substr(2,8),2)+
        parseInt(d.substr(10,8),2)+
        parseInt(d.substr(18,8),2)+
        parseInt(d.substr(26,8),2);
    console.log('n=',n,'len=',d.length,' cks=',cks&0xFF,' chsum=',parseInt(d.substr(34,8),2));
    if (cks&&((cks&0xFF)==parseInt(d.substr(34,8),2))) {

The example code

var dht=new DHT22(dpin);

setInterval(function () {
  dht.read(function (a) {
 F=a.temp;
 H=a.rh;
  console.log("Temp is "+F.toString()+" and RH is "+H.toString());
});
}, 2000);

Produces the following output:

n= 3 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 0  cks= 0  chsum= NaN
n= 6 len= 0  cks= 0  chsum= NaN
n= 9 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 5 len= 0  cks= 0  chsum= NaN
n= 4 len= 42  cks= 202  chsum= 202
Temp is 23.2 and RH is 48.1
n= 10 len= 42  cks= 202  chsum= 202
Temp is 23.2 and RH is 48.1
n= 10 len= 42  cks= 202  chsum= 202
Temp is 23.2 and RH is 48.1
n= 10 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 40  cks= 200  chsum= 50
n= 9 len= 41  cks= 200  chsum= 100
n= 8 len= 41  cks= 200  chsum= 100
n= 7 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 0  cks= 0  chsum= NaN
n= 9 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 42  cks= 202  chsum= 202
Temp is 23.2 and RH is 48.1
n= 10 len= 42  cks= 201  chsum= 201
Temp is 23.2 and RH is 48

Notice that the module code produces a lot of retries n. 1st try n=10, 2nd try n=9...

By changing the example code to

var dht=new DHT22(dpin);
setInterval(function () {
  dht.read(function (a) {});
  dht.read(function (a) {
 F=a.temp;
 H=a.rh;
  console.log("Temp is "+F.toString()+" and RH is "+H.toString());
});
}, 2000);

Which gives to following output

>echo(0);
=undefined
n= 10 len= 43  cks= 201  chsum= 201
n= 10 len= 43  cks= 201  chsum= 201
Temp is 23.2 and RH is 48
n= 10 len= 43  cks= 199  chsum= 199
n= 10 len= 43  cks= 199  chsum= 199
Temp is 23.2 and RH is 47.8
n= 10 len= 43  cks= 198  chsum= 198
n= 10 len= 43  cks= 198  chsum= 198
Temp is 23.2 and RH is 47.7
n= 10 len= 43  cks= 198  chsum= 198
n= 10 len= 43  cks= 198  chsum= 198
Temp is 23.2 and RH is 47.7
n= 10 len= 43  cks= 198  chsum= 198
n= 10 len= 43  cks= 198  chsum= 198
Temp is 23.2 and RH is 47.7
n= 10 len= 43  cks= 199  chsum= 199
n= 10 len= 43  cks= 199  chsum= 199
Temp is 23.2 and RH is 47.8
n= 10 len= 43  cks= 199  chsum= 199
n= 10 len= 43  cks= 199  chsum= 199
Temp is 23.2 and RH is 47.8
n= 10 len= 43  cks= 199  chsum= 199
n= 10 len= 43  cks= 199  chsum= 199
Temp is 23.2 and RH is 47.8

This gives correct temperature and humidity readings without all the retries in the module code. From a programming perspective it is troubling as Gordon outlined above.
Even with the setInterval =1000.

And finally changing the example code one more time so that the one dht.read completes before the 2nd one starts.

//var dht = require("DHT22").connect(dpin);
var dht=new DHT22(dpin);
setInterval(function () {
  dht.read(function (a) {//});
  dht.read(function (a) {
 F=a.temp;
// F=(a.temp+40)*9/5-40;
 H=a.rh;
  console.log("Temp is "+F.toString()+" and RH is "+H.toString());
});
    });
}, 2000);

This gives;

=undefined
n= 10 len= 40  cks= 199  chsum= 49
n= 9 len= 42  cks= 197  chsum= 197
n= 10 len= 0  cks= 0  chsum= NaN
n= 9 len= 41  cks= 198  chsum= 99
n= 8 len= 42  cks= 197  chsum= 197
Temp is 23.2 and RH is 47.6
n= 10 len= 0  cks= 0  chsum= NaN
n= 9 len= 41  cks= 198  chsum= 99
n= 8 len= 41  cks= 198  chsum= 99
n= 7 len= 41  cks= 198  chsum= 99
n= 10 len= 0  cks= 0  chsum= NaN
n= 6 len= 41  cks= 198  chsum= 99
n= 9 len= 0  cks= 0  chsum= NaN
n= 5 len= 41  cks= 198  chsum= 99
n= 8 len= 0  cks= 0  chsum= NaN
n= 4 len= 42  cks= 197  chsum= 197
n= 10 len= 0  cks= 0  chsum= NaN
n= 7 len= 0  cks= 0  chsum= NaN
n= 9 len= 42  cks= 197  chsum= 197
Temp is 23.2 and RH is 47.6
n= 10 len= 0  cks= 0  chsum= NaN
n= 6 len= 0  cks= 0  chsum= NaN
n= 9 len= 42  cks= 197  chsum= 197
n= 10 len= 0  cks= 0  chsum= NaN
n= 5 len= 0  cks= 0  chsum= NaN
n= 4 len= 1  cks= 0  chsum= NaN
n= 9 len= 43  cks= 197  chsum= 197
Temp is 23.2 and RH is 47.6

Changing the set interval from 1000 to 2000 helps.
On a scope the entire message takes just under 6ms.