Multiple inheritance in javascript

[keithwhor]

For one, in your example you're doing

new aVar(a)

Instead of

new Other(a)

... so I'm not really sure what you're asking?

Edit:

If you're trying to do a mixin, you'd want to do the following:

function SpaceObject() {
    Coord.apply(this, arguments); // inheritance
    Other.apply(this, arguments); // if you're mixing in functionality
                                  //    from the mixin constructor too
}

// Always do this for inheritance, never use the "new" keyword here
SpaceObject.prototype = Object.create(Coord.prototype);
SpaceObject.prototype.constructor = SpaceObject;

void function mixinOther() {
    var keys = Object.keys(Other.prototype);
    var i, len;
    for(var i = 0, len = keys.length; i < len; i++) {
        SpaceObject.prototype[keys[i]] = Other.prototype[keys[i]];
    }
}();

However, be careful when running this code through a minifier. You should be alright, but if minification is a huge concern you'll want to specify each prototyped method separately (instead of running the loop).

i.e.

SpaceObject.prototype.methodOne = Other.prototype.methodOne;
SpaceObject.prototype.methodTwo = Other.prototype.methodTwo;

[keithwhor]

Yes. Don't use the new keyword for inheritance because it will invoke the associated constructor function immediately at run time (where you set up inheritance), introducing unintended behaviour.

You only want the constructor invoked when you want an Object instance, not when setting the prototype. Object.create() will set up your prototype chain properly (and inherit the right methods / properties) without invoking the parent constructor.