How to create this kind of Object in Javascript

Question

I'm using Node.js to access this hdPrivateKey but it look like

 <hdPrivateKey...>

Not look like normal JS object.

And console.log(address) looks like

<Address: 19o9ghmkUrNVf4d57tQJuUBb2gT8sbzKyq, type: pubkeyhash, network: livenet>

console.log(Object.keys(address)) look like

[ 'hashBuffer', 'network', 'type' ]

Why the key inside address are different?

var bitcore = require('bitcore');
var HDPrivateKey = bitcore.HDPrivateKey;

var hdPrivateKey = new HDPrivateKey();
console.log(hdPrivateKey)
var retrieved = new HDPrivateKey(hdPrivateKey);
var derived = hdPrivateKey.derive("m/0");
var derivedByNumber = hdPrivateKey.derive(1).derive(2, true);
var derivedByArgument = hdPrivateKey.derive("m/1/2");

var address = derived.privateKey.toAddress();
console.log(Object.keys(address))
console.log(address)
// obtain HDPublicKey
var hdPublicKey = hdPrivateKey.hdPublicKey;

I found this useful link github.com/nodejs/node/issues/8071. — Chien Lee
– Chien Lee, Commented Jan 22, 2018 at 14:32

T.J. Crowder · Accepted Answer · 2018-01-22 14:19:00Z

1

The behavior you're seeing is because the object has its own inspect property which is a function and returns a string. When console.log sees that it's logging an object, it looks for that function and uses it if available. So on Node, this logs <foo>:

const o = {
    inspect() {
        return "<foo>";
    }
};
console.log(o);

That's all that the HDPrivateKey object is doing.

If you want to properly inspect the object, use a debugger. Alternately, use utils.inspect with customInspect set to false.

answered Jan 22, 2018 at 14:19

T.J. Crowder

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1 Comment

Chien Lee Over a year ago

Thanks for this answer.

Arkerone · Accepted Answer · 2018-01-22 14:18:30Z

1

In Node.js, a console.log call the function inspect of the object. In the bitcore-lib there is this method :

HDPrivateKey.prototype.inspect = function() {
  return '<HDPrivateKey: ' + this.xprivkey + '>';
};

And this method:

Address.prototype.inspect = function() {
  return '<Address: ' + this.toString() + ', type: ' + this.type + ', network: ' + this.network + '>';
};

answered Jan 22, 2018 at 14:18

Arkerone

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1 Comment

Chien Lee Over a year ago

Thanks for this answer.

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