factories versus libraries

[Andrew Poulos]

If I have a "factory" that is in this form:

function ma() {
blah;
}
ma.prototype.a = function() {
blah2;
}
var obj = new ma()

and I have a "library" that's of this form:

ma = {
a: function() {
blah2;
},
b: blah;,
}

Is there any advantage using one over the other? I've done a google and
have found out some things about both but I don't have enough
programming theory to make a decision.
Andrew Poulos

[Martin Honnen]

Andrew Poulos wrote:

If I have a "factory" that is in this form:

function ma() {
blah;
}
ma.prototype.a = function() {
blah2;
}
var obj = new ma()

and I have a "library" that's of this form:

ma = {
a: function() {
blah2;
},
b: blah;,
}

Is there any advantage using one over the other?

With the first version you can instantiate as much objects having the
same method a as needed e.g.
var ma1 = new ma();
var ma2 = new ma();
The second version creates exactly one object having a method a. If you
only want one object of that "type" then the second version suffices but
if you want to created several objects of a "type" then the first
version is what you need.
--

Martin Honnen
http://JavaScript.FAQTs.com/

[Douglas Crockford]

> If I have a "factory" that is in this form:

function ma() {
blah;
}
ma.prototype.a = function() {
blah2;
}
var obj = new ma();
What you have there is a constructor.
See http://www.crockford.com/javascript/inheritance.html
and I have a "library" that's of this form:

ma = {
a: function() {
blah2;
},
b: blah;,
}
What you have there is an object made using the object literal notation.
See http://www.crockford.com/javascript/survey.html and http://www.JSON.org
Is there any advantage using one over the other? I've done a google and
have found out some things about both but I don't have enough
programming theory to make a decision.

Which to use depends on how many objects you are going to be producing.
If you need a lot of them, it makes sense to have a constructor. If you
need only one, it makes sense to make a single object.