Minimalist Classes

Brendan Eich brendan at
Wed Nov 2 11:29:23 PDT 2011

On Nov 2, 2011, at 11:17 AM, David Bruant wrote:

>> See my reply to Kam. We're not sugaring instance-private ivars. I am proposing something we agreed to in Nov. 2008: sugaring class-private ivars.
> Ok, that's what I was missing. What were the rationale? use cases?

The rationale is that most mainstream OO languages with the most users support class-private not instance-private ivars. Sorry, Smalltalkers!

Use cases are all around us in JS today, using public properties. Refactoring to private should not require rewriting to add getter/setter method, etc.

>> You can make instance-private ivars yourself in the constructor using Name.create, and go to town. Knock yourself out! (I mean that in a good way, at least from where I sit :-P).
> Hmm... Are you sure you can implement instance-private variables with no
> leak?

You'd need to use the closure pattern:

class BnD {
  constructor(x) {
    const my_x = Name.create('x');
    this[my_x] = x;
    this.method1 = function (...) {...};
    this.methodN = function (...) {...};

The method1..N functions can use my_x, no one else can.

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