This document discusses challenges with enumerating over native JavaScript objects and some techniques for overcoming those challenges to emulate array-like behavior. It describes how ES5 methods don't work directly on objects, issues with iteration order and the length property, and presents a solution for encapsulating an object with array enumeration methods by defining indexed properties based on the object's properties. The solution allows treating objects like arrays while retaining key-value pairs and ordering.

1. ENUMERABLE.JSENUMERABLE.JSENUMERABLE.JSENUMERABLE.JSENUMERABLE.JSENUMERABLE.JS

2. ES5 IS NOT OPERATING ON NATIVE OBJECTS

3. WE CAN'T CALL ES5 METHODS IN OBJECT CONTEXT
alert([].map.call({head:15,title:30},function(s){return s+'px'}).join(', '))

4. SOMETIMES WE CAN, HOLY GRAIL..
var o={foo:"foo"}
Array.push(o, 'foo');
Array.push(o, bar);
alert( o.toSource() );//prints:({foo:"foo", length:1, 1:"bar"})

5. SOMETIMES WE MISUNDERSTOOD ARGUMENTATIONS
var r=
[
{id:0,title:'poem'}
].
filter(function(book){
alert(book.id+" : "+book.title+" : "+this.author);
return book.id==4
},
{author:'Shakespeare'});

6. WHERE HAS MY AUTHORS DISAPPEARED?
r.forEach(function(book){
alert(book.id+" : "+this.author);//prints 0+" : "+undefned
})

7. "HOW ABOUT EMULATING AN ARRAY INSIDE AN OBJECT?"
@Angus Croll

8. WE WILL HAVE TROUBLE WITH LENGTH

9. LET'S ITERATE THROUGH OBJECT TO MIMIC INDEX
var index = 0;
for(var prop in this){
if(!this.__lookupGetter__(prop) &&
this.constructor!=Array){
(function(thisIndex, thisProp){
Object.defineProperty(obj, thisIndex, {
get: function(){return obj[thisProp]}
, enumerable: true
, configurable: true
, writeable: true
});
})(index, prop)
index++;
}
}

10. UPDATE OBJECT
Object.defineProperty(obj, 'length', {
get: function(){
return obj.update();
}
set: function(){
return obj.update();
}
, configurable : false
, enumerable : false
, writeable : true
});
obj.length;

11. CCCHHHEEECCCKKK TTTHHHEEE SSSOOOUUURRRCCCEEE DDDUUUDDDEEE!!!

12. WORKS?
var myObj={jozsi:2,tamas:5};
//wrap up our object extensional expressions to a method;
extendObj_as_array(myObj);
alert('myObj is now an emulated kind of array '+myObj.length);
//adding new, uninitialized property also as array indices;
myObj.aron=0;

13. NO...
//it is not possible to query the newly added index to myObj,
//because index is actually uninitialized until the length is queried;
alert('newly added index is undefined: '+myObj[2]);
//length is queried, indices are being updated!
alert('indices are updated: '+myObj.length);
//Now it is possible to query the newly added index to myObj;
alert('newly added index is now defined: '+myObj[2]);
//array functionality works on objects;
alert('mapping values as pixels: '+
[].map.call(myObj,function(s){return s+'px'}).join(', '));
//prints "2px, 5px, 0px"

14. OBJECT IS KEY-VALUE PAIR RETAINING THE ORDER

15. SO ENCAPSULATE DIFFERENCES!
var enum=enumerable();
var enum=enumerable([]);
var enum=enumerable({});
var enum=enumerable(new enumerable);

16. LET US WORK!
//note! vacuum.db.tables[table] is a valid JavaScript Object.
enumerable(vacuum.db.tables[table]).
sort({againstVal:true,func:function(a,b){return a.frequency<b.frequency}}).
.forEach(function(i,val){
if(it.isTypeOf(val,[Object]).
ANDNOT({macro:'$this.id=='+self.defaultRecord}).true())
{
self.record(table,val.id);
}
return true;
});

17. FEATURES & PRINCIPLES
functional break support
Undo-redo transactions
Recursion support
returning interface consistency
Rock solid ordering management

18. FEATURES BASED ON ORDERING
Comparison between different types
Order based comparisons
fromItem/toItem support(bubbling)

19. BIBLIOGRAPY
Angus Croll
HTMLpiknik
Problems with extending regular Objects
enumeration order guarantee