EDIT: I figured it out from Bergi's answer in the end.
Thanks Bergi.
pubPrivExample = (function () {
return {
init : function () {
var private;
this.setPrivate = function (p) {
private = p;
};
this.getPrivate = function () {
return private;
};
},
public : "This is public\n"
};
}());
var a;
a = Object.create(pubPrivExample);
a.init();
a.setPrivate("This is private");
document.write(a.getPrivate());
EDIT: It seems the answers to my question are off at a tangent. I'm really not interested in a factory and actually would rather not use if. My question is about private state. From Bergi's answers and comments I think I can pull something together.
To be continued...
EDIT: Bergi has started to answer the question below, but left out the most important part - the private state.
I have had time to think about the idea more, but am still unable to achieve private state using Object.create() without some kind of factory. But I want to be wrong, and Bergi alluded to a solution... Feel free to take Bergi's answer as a starting point.
ORIGINAL: My quest to avoid new
in javascript has lead me to a peculiar place. I want private object members, but I don't want to give up Object.create()
.
Here's the code.
var trackQueue = {};
trackQueue.factory = function () {
var that, queue;
that = this;
queue = [];
that.push = function (item) {
queue.push(item);
};
that.work = function () {
document.write(queue + "<br />");
};
return {
work : that.work,
push : that.push
};
};
var a = Object.create( trackQueue.factory() );
a.push("a");
a.push("b");
a.push("c");
var b = Object.create( trackQueue.factory() );
b.push("d");
b.push("e");
b.push("f");
a.work();
b.work();
And a jsfiddle
http://jsfiddle.net/dsjbirch/Wj6cp/10/
Would init
be a more idiomatic / appropriate name for the factory
method?
Is this insane?
Be kind - javascript isn't my first language.
Creating a JavaScript Object Create a single object, with the keyword new . Define an object constructor, and then create objects of the constructed type. Create an object using Object.create() .
The Object() Constructor JavaScript provides a special constructor function called Object() to build the object. The new operator is used to create an instance of an object. To create an object, the new operator is followed by the constructor method. Following is the syntax for defining an object.
Create method is used to create object instance with an already declared object properties and it's prototype and assign it to a newly created prototype object and return's empty object. Assign method is used to assign object properties from source object to the target object and also return's the new object.
Yes, a init method on the prototype might be a more appropriate name:
var proto = {
init: function(args) {
// setting up private-scoped vars,
var example = args;
// privileged methods
this.accessPrivate = function(){ return example; };
// and other stuff
this.public = 5;
},
prop: "defaultvalue",
...
}
var instance = Object.create(proto);
instance.init();
However, there is absolutely no reason not to use the classical constructor with the new keyword, which elegantly combines the Object.create
and init
call.
And note that you are using Object.create
with absolutely no use. Your factory pattern (perfectly valid applied) returns good objects. No need to create new objects for each one that inherit from them. Just do:
var instance = trackQueue.factory();
If you like the sound of the method name "create", you might use a more idiomatic name for your factory:
trackQueueFactory.create = function(args) {...};
EDIT: Your idea to combine the factory pattern with prototype inheritance is not so wrong. Yet, the proto object from which all the fabricated objects inherit needs to be static, instead of creating a new one on each invocation. Your code might look like this:
var factory = {
proto: {
...
},
create: function(args) {
var product = Object.create(this.proto);
// set up private vars scoped to the create function
// privileged methods
product.doSomethingSpecial = function(){ ... };
// and other stuff
}
};
var a = factory.create(...);
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