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_xt

Super lightweight prototype extend library
No class or static keywords
No heavy thousands of clones
No heavy magic this.super()
just prototype inheritance

_xt.extend(A, B)

assign to constructor A a new instance of function B as its prototype

(new A) instanceof B === true

_xt.extend(A, B, C)

assign to constructor A a new instance of function B as its prototype

(new A) instanceof B === true

assign to the new instance of B, a singleton instance of C as its prototype and store it in A._xxt

(new A) instanceof C === true
A._xxt instanceof C === true

_xt.extend(A, B, C);
_xt.extend(A2, B2, C);
//the expressions below are true
A2._xxt === A._xxt
A2._xxt.constructor === A._xxt.constructor === C

if B and C set a property object called options, the prototype of A will have the merged options of C into B. We could have called it 'static'.

var A = function(){};
var C = function(){
  this.options = {
    option1: true,
    option2: true
  }
_xt.extend(A, function(){
  this.options = {
    option1: false,
    option3: true
  }
}, C);

(new A).options => 
{
  option1: false,
  option2: true,
  option3: true
}

new A does not call C as constructor. You have to do it manually, this is also true for instance methods.

var A = function(){
  A._xxt.constructor.apply(this, arguments);
};
var C = function(){
  this.which = function(){
    return C._xxt.method.call(this) + 'c';
  };
};
_xt.extend(A, function(){
  this.which = function(){
    return A._xxt.method.call(this) + 'a';
  };
}, C);

(new A).which() === 'ca';

This is not magic as the super() method you can see in other libs
But it's fast.

_xt.extend(A, B, C, D, E)

_xt.extend(A, B, C)

But it mixins in A.prototype the D and E objects or prototypes if D and E are functions.

var D = function(){
  this.d = true;
}
_xt.extend(D, function(){
  this.beCareful = true;
  this.isD = function(){
    return true;
  }
});
_xt.extend(A, B, C, D);
var a = new A();

//the expressions below are true
a instanceof C
!(a instanceof D)
a.isD()
a.beCareful
a.d === undefined

You probably want a.d to be true but the mixins constructors are not automatically called. We must modify A to call all its mixins constructors.

var A = function(){
  _xt.constructMixins(this);
}

(new A).d === true

This works because _xt.mixin stores each mixin in an array (this._mixins). ConstructMixins is useful when you have a deep inheritance with many mixins attached. For more granularity, this works as well:

var A = function(){
  D.constructor.call(this);
}

You should be careful when using mixins because the mixin is attached to a prototype potentially used by many others instances. For example, _xt.Notifier is a very simple pubsub constructor which uses an object to store the event handlers.

_xt.Notifier = function(){ this._events = {} };

_xt.extend(A, Pa, null, _xt.Notifier);
_xt.extend(B, Pb, A);
_xt.extend(C, Pc, A);
var a = new A, b = new B, c = new C;

The following is true but you don't want it

a._events === b._events === c._events

Because b.attachEvent('change', bChangeHandler) attach the handler to the change event of a, b and c
a.fireEvent('change') will execute bChangeHandler which is probably not the right behavior
You must think if the constructors should or should not be called.

_xt.mixin(A, B, C, ..)

Equivalent to

_xt.extend(A, Pa, null, B, C, ...)

See the doc above

_xt.constructMixins(obj)

Call the constructor of each mixin attached to obj passing obj as 'this'. The mixins are stored in obj._mixins.

_xt.merge(obj, obj2, obj3, ...)

Assign all the enumerable properties of obj2, obj3, ... to obj. The replacement is from right to left. It is not a clone.

obj1.x = 1;
obj2.x = 2;
obj3.x = 3;
obj3.prop = { merged: false };
_xt.merge(obj1, obj2, obj3);
obj1.prop.merged = false;
//expressions below are true
obj1.x === 3;
obj3.prop === obj1.prop;
obj3.merged = false;

_xt.mergeProp(obj, propPath, propValue)

Merge a path ('prop1.subProp1.subProp2') in obj and set the propValue so that obj.prop1.subProp1.subProp2 === propValue If propValue and objpropPath are both objects, they are merged with _xt.merge, else the value is replaced or created.