How to pass custom class instances through Web-Workers?

Question

Since Web-Worker JSON serialize data between threads, something like this doesn't work:

worker.js

function Animal() {}
Animal.prototype.foobar = function() {}

self.onmessage = function(e) {
  self.postMessage({animal: new Animal()})  
}

main.js

let worker = new Worker('worker.js')

worker.onmessage = function(e) {
    console.log(e.data)
}

worker.postMessage('go!')

The outcome would be a simple object with the loss of the foobar prototype method.

Is it possible to transfer the custom object back to the main thread without losing its prototype methods? Like, would this be possible with ArrayBuffer? I'm not familiar with that stuff, so I'm a bit lost.

Answer 1

1. Assuming you program both the client and the webservice you can define the Animal function in boths sides
2. Then you can add to Animal.prototype (in both sides) toJson method to pass the info you need to recreate the object (and may be choose some attribute to define the className)
3. You define a reviver that use the reverse process
4. Then when you post you must always JSON.stringify(e)

5. In the onmessage you JSON.parse(m,reviver)

   function Animal(name, age){
      var private_name = name;
      this.public_age = age;
      this.log = function(){
        console.log('Animal', private_name, this.public_age);
      }
      this.toJson = function(){
        return JSON.stringify({
          __type__:'Animal',  // name of class
          __args__:[this.public_age, private_name] // same args that construct
        });
      }        
   }
   
   Animal.prototype.age = function(){
      return this.public_age;
   }
   
   var a = new Animal('boby', 6);
   
   worker.postMessage(JSON.stringify(a));
   
   function reviver(o){
     if(o.__type__){
       var constructor=reviver.register[o.__type__];
       if(!constructor) throw Error('__type__ not recognized');
       var newObject = {};
       return constructor.apply(newObject, o.__args__);
     }
     return o;
   }
   
   reviver.register={}; // you can register any classes
   
   reviver.register['Animal'] = Animal;
   
   worker.onmessage = function(m){
     var a = JSON.parse(e, reviver);
   }