library cbor introduces a new value in the conversion

I made on node.js, this program, which has an anomaly. When I do decodeAllSync I get a vector of decimal numbers which has one fewer numbers than I get by reconverting the vector with encodeAsync. Why don't I get the same vector? Thank you

const cbor = require('cbor');
...
const results = cbor.decodeAllSync(output);
const input = cbor.encodeAsync(results);
console.log(output);
input.then( 
    function (x) {
      var v=new Uint8Array(x);
      console.log(v);
    },
    function () {
      console.log("fail ");
    });

I receive for the printout of the input:

Uint8Array [
  129,
  210,
  132,
  77,
  ...

I receive for the printout of the output:

Uint8Array [
  210,
  132,
  77,
  ...

cbor.decodeAllSync with n arguments returns an array with n entries. So what you encode has an extra pair of [] around it.

> cbor.decodeAllSync(cbor.encode(1))
[ 1 ]
> cbor.decode(cbor.encode(1))
1