On Fri, Dec 11, 2009 at 12:08 PM, Mike Wilson <mike...@hotmail.com> wrote:
> Mark S. Miller wrote:
>
> If we're looking for a convention that is
> * does not admit any legacy ES3R non-array non-host objects (to prevent
> false positives)
No native ES objects?
> * does easily allow ES5 programmers to define new array-like non-array
> objects
> * takes bounded-by-constant time (i.e., no iteration)
*What* takes bounded-by-constant time? The object's existence would
not take any time.
> * is a reasonably compatible compromise with the existing notions of
> array-like in legacy libraries as represented by previous examples in this
> thread
Can you please clarify what the problem area is a little more?
> then I suggest:
> function isArrayLike(obj) {
> var len;
> return !!(obj &&
> typeof obj === 'object' &&
> 'length' in obj &&
> !({}).propertyIsEnumerable.call(obj, 'length') &&
> (len = obj.length) >>> 0 === len);
> }
>
Is looks like "array like" is defined as an an object where "length"
is non-enumerable and numeric. What about [[Get]], [[HasProperty]] for
numeric property names?
And why must the - length - property be an *own* property? Why could
length not be a getter in the prototype chain?
Indeed many Mozilla DOM collections work this way:
javascript: var cn = document.links; alert([cn.length,
({}).hasOwnProperty.call( cn, "length")]);
Mozilla elerts "80, false"
Garrett
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