constructors part 2 electric boogaloo

src/js/internal/streams/duplex.js

@@ -40,6 +40,8 @@ const { kOnConstructed } = require("internal/streams/utils");
 function Duplex(options) {
   if (!(this instanceof Duplex)) return new Duplex(options);
 
+  this.constructor = Duplex;
+
   this._events ??= {
     close: undefined,
     error: undefined,

src/js/internal/streams/legacy.js

@@ -8,6 +8,7 @@ const EE = require("node:events");
 
 function Stream(opts) {
   EE.$call(this, opts);
+  this.constructor = Stream;
 }
 Stream.constructor = Stream;
 

src/js/internal/streams/passthrough.js

@@ -37,6 +37,8 @@ ObjectSetPrototypeOf(PassThrough, Transform);
 function PassThrough(options) {
   if (!(this instanceof PassThrough)) return new PassThrough(options);
 
+  this.constructor = PassThrough;
+
   Transform.$call(this, options);
 }
 

src/js/internal/streams/readable.js

@@ -311,6 +311,7 @@ ReadableState.prototype[kOnConstructed] = function onConstructed(stream) {
 function Readable(options) {
   if (!(this instanceof Readable)) return new Readable(options);
 
+  this.constructor = Readable;
   this._events ??= {
     close: undefined,
     error: undefined,

src/js/internal/streams/transform.js

@@ -77,6 +77,8 @@ const kCallback = Symbol("kCallback");
 function Transform(options) {
   if (!(this instanceof Transform)) return new Transform(options);
 
+  this.constructor = Transform;
+
   // TODO (ronag): This should preferably always be
   // applied but would be semver-major. Or even better;
   // make Transform a Readable with the Writable interface.

src/js/internal/streams/writable.js

@@ -388,6 +388,7 @@ WritableState.prototype[kOnConstructed] = function onConstructed(stream) {
 function Writable(options) {
   if (!(this instanceof Writable)) return new Writable(options);
 
+  this.constructor = Writable;
   this._events ??= {
     close: undefined,
     error: undefined,