I wonder if we could get most of the benefits of class initializers, but
approach the issue from the object side. I have no intent of launching a
competing proposal (given that I don’t understand all the issues that are
involved), but just wanted to put the idea out there.
= Parameterized object literals (POLs) =
Parameterized object literals are a more stylized version of functions that
return object literals.
If they assign a prototype, they can be used to implement types.
function f(a,b) {...} becomes object f(a,b) {...}
function(a,b) {...} becomes object(a,b) {...}
object Point(x,y) {
__proto__: {
dist: function() {
return Math.sqrt((x*x)+(y*y));
}
},
x: x,
y: y,
}
object Colored(color) {
__proto__: {
describe: function() {
return "Color: "+this.color;
}
},
color: color
}
// *Not* multiple inheritance (linear chain of types!)
object ColoredPoint(x, y, color)
extends Point(x,y), Colored(color) {
}
Comments:
- __proto__ is a pseudo-property that can only be set once.
- Getters and setters work like in object literals.
- Still needed: defining property attributes (writable, configurable,
enumerable) directly in object literals.
- Possible: init() method that performs additional computations.
Algorithm for type chaining:
- Collect all prototypes (if any) and chain (copies of) them
- Assign the combined prototype to __proto__ (no prototypes => do nothing)
- Chain the parameterized object literals in a similar manner
Similar to POLs: class initializers [1]:
- Main difference: POLs approach the issue from the object side and increase
the declarativeness of what would be the new() method in class initializers.
- Advantage: there is no need to introduce the concept of classes in JavaScript.
[1]
http://wiki.ecmascript.org/doku.php?id=strawman:obj_initialiser_class_abstraction
--
Dr. Axel Rauschmayer
[email protected]
twitter.com/rauschma
home: rauschma.de
blog: 2ality.com
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
