Saturday, November 12, 2011

Few JavaScript Patterns

Just to be clear and once again, JavaScript can emulate:
  • classes
  • public and public static methods or properties
  • private and private static methods or properties
  • public and private constants
  • protected methods
  • ... you name it ...

// duck typing ( maybe all you need )
var me = {name: "WebReflection"};

// basic class
function Person() {}
Person.prototype.getName = function () {
return this.name;
};
Person.prototype.setName = function (name) {
this.name = name;
};

// module pattern + private properties / methods
function Person(_name) {
function _getName() {
return _name;
}
return {
getName: function () {
// redundant, example only
return _getName();
},
setName: function (name) {
_name = name;
}
};
}

// private shared methods via this
var Person = (function () {
function Person() {}
function _getName () {
return this.name;
}
function _setName (name) {
this.name = name;
}
Person.prototype.getName = function () {
return _getName.call(this);
};
Person.prototype.setName = function (name) {
_setName.call(this, name);
};
return Person;
}());

// private shared method Python style
var Person = (function () {
function Person() {}
function _getName (self) {
return self.name;
}
function _setName (self, name) {
self.name = name;
}
Person.prototype.getName = function () {
return _getName(this);
};
Person.prototype.setName = function (name) {
_setName(this, name);
};
return Person;
}());

// public static
function Person() {
Person.TOTAL++;
}
Person.TOTAL = 0;

// private static / constant
var Person = (function () {
var TOTAL = 0;
return function Person() {
TOTAL++;
};
}());

// public constant
function Person() {}
Object.defineProperty(Person, "RACE", {
writable: false, // default
configurable: false,// default
enumerable: true,
value: "HUMAN"
});

// public inherited constant
function Person() {}
Object.defineProperty(Person.prototype, "RACE", {
writable: false, // default
configurable: false,// default
enumerable: true,
value: "HUMAN"
});

// protected method
function Person() {}
Person.prototype.getName = function () {
return this instanceof Person ?
this.name :
throw "protected method violation"
;
};
Person.prototype.setName = function (name) {
this instanceof Person ?
this.name = name :
throw "protected method violation"
;
};

// generic protected methods
Function.prototype.protectedVia = function (Class) {
var method = this;
Class || (Class = Object);
return function () {
if (this instanceof Class) {
return method.apply(this, arguments);
}
throw "protected method violation on " + (
Class.name || Class
);
};
};
function Person() {}
Person.prototype.getName = function () {
return this.name;
}.protectedVia(Person);
Person.prototype.setName = function (name) {
this.name = name
}.protectedVia(Person);

// private shared variables
function Person() {}
Person.prototype.getName = function () {
return this.name;
};
(function (PersonPrototype) {
var changes = 0;
PersonPrototype.setName = function (name) {
changes++;
this.name = name;
};
PersonPrototype.howManyChangedName = function () {
return changes;
};
}(Person.prototype));

// getters / setters on public property
var person = Object.defineProperty({}, "name", {
get: function () {
return this._name;
},
set: function (_name) {
this._name = _name;
}
});

// getters setters on public property via prototype
function Person() {}
Object.defineProperty(Person.prototype, "name", {
get: function () {
return this._name;
},
set: function (_name) {
this._name = _name;
}
});

// getters / setters on private property
var person = Object.defineProperty({}, "name", (function () {
var _name;
return {
get: function () {
return _name;
},
set: function (name) {
_name = name;
}
};
}()));

// singleton
var me = {name: "WebReflection"};

// singleton via anonymous __proto__
// plus private properties
var me = new function () {
var _name;
this.getName = function () {
return _name;
};
this.setName = function (name) {
_name = name;
};
};

// generic singleton cross browser
Function.prototype.singleton = (function () {
function anonymous(){};
function create(Class, args) {
anonymous.prototype = Class.prototype;
Class.apply(
Class.__singleton__ = new anonymous,
args
);
return Class.__singleton__;
}
return function singleton() {
return this.__singleton__ || create(this, arguments);
};
}());

// generic singleton ES5
Function.prototype.singleton = (function () {
function create(Class, args) {
Class.apply(
Class.__singleton__ = Object.create(
Class.prototype
), args
);
return Class.__singleton__;
}
return function singleton() {
returh this.__singleton__ || create(this, arguments);
};
}());

// per function private singleton
var Person = (function () {
var instance;
return function Person () {
return instance || (instance = this);
// or ... ot be more than sure ...
return instance || (
(instance = true) && // avoid infinite recursion
(instance = new Person)
);
};
}());

// generic factory
Function.prototype.factory = (function () {
function anonymous() {};
return function factory() {
anonymous.prototype = this.prototype;
var instance = new anonymous;
this.apply(instance, arguments);
return instance;
};
}());

// generic factory ES5 + ruby style
Function.prototype.new = function factory() {
var instance = Object.create(this.prototype);
this.apply(instance, arguments);
return instance;
};

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