util.inherits - alternative or workaround

Question

I am a n00b in node, and find util.inherits() very useful, except for the fact that it seems to replace the entire prototype of the original object. For instance:

var myClass = function(name){
    this._name = name;  
};

myClass.prototype = {
    (...)
};

util.inherits(myClass, require('events').EventEmitter);

seems to erase my original prototype.

That brings me two inconveniences:
1 - I have to declare add properties to my prototype after calling inherits,

var myClass = function(name){
    this._name = name;  
};

util.inherits(myClass, require('events').EventEmitter);

myClass.prototype.prop1 = function(){...};
myClass.prototype.prop2 = function(){...};

and, most important, i think i cannot inherit from two or more different classes.

Can anyone explain to me why this makes sense and what would be a good way to work around this?

Thanks

Answer 1

It does not make sense that you have to declare your prototype after util.inherits(). My guess is util.inherits originated as an internal-use-only method, tailored only for the limited internal use-cases it was initially intended for, which at some point got published for general usage. The util module is written in pure JS, so it is very easy to implement your own version of util.inherit that preserves your prototype. Here's the original util.inherit source:

exports.inherits = function(ctor, superCtor) {
  ctor.super_ = superCtor;
  ctor.prototype = Object.create(superCtor.prototype, {
    constructor: {
      value: ctor,
      enumerable: false,
      writable: true,
      configurable: true
    }
  });
};

As for the multiple inheritance, that's going to be a much more difficult problem to tackle, as Javascript's prototype inheritance is not really suited for multiple inheritance at all. Each instance has only a single internal [[Prototype]] property, which is used to look up members that are not found in the actual instance. You could merge the prototypes of two separate "parent classes" into a single prototype, but you will then lose the inheritance to their parents, and you will lose the ability to change the parent prototype and have all children see the change.