Account Options

  1. Sign in
The old Google Groups will be going away soon, but your browser is incompatible with the new version.
Google Groups Home
« Groups Home
comp.lang.javascript
+ new post
About this group
Subscribe to this group
This is a Usenet group - learn more
Message from discussion "x.constructor == Foo" vs "x instanceof Foo"
The group you are posting to is a Usenet group. Messages posted to this group will make your email address visible to anyone on the Internet.
Your reply message has not been sent.
Your post was successful
 
From:
To:
Cc:
Followup To:
Add Cc | Add Followup-to | Edit Subject
Subject:
Validation:
For verification purposes please type the characters you see in the picture below or the numbers you hear by clicking the accessibility icon. Listen and type the numbers you hear
 
Joost Diepenmaat  
View profile  
 More options Jan 28 2008, 4:58 pm
Newsgroups: comp.lang.javascript
From: Joost Diepenmaat <jo...@zeekat.nl>
Date: Mon, 28 Jan 2008 22:58:40 +0100
Local: Mon, Jan 28 2008 4:58 pm
Subject: Re: "x.constructor == Foo" vs "x instanceof Foo"
Print | View thread | Show original | Report this message | Find messages by this author
Thomas 'PointedEars' Lahn <PointedE...@web.de> writes:

> Joost Diepenmaat wrote:
>> Thomas 'PointedEars' Lahn <PointedE...@web.de> writes:
>>> Thanks, I was looking for that.  However, you should consider that the
>>> increased runtime efficiency gained by declaring the Dummy() constructor
>>> only once is mitigated by the reduced memory efficiency caused by the
>>> continued allocation of memory due to the closure.  And since there are
>>> more issues with closures than without them, I would avoid them here.

>> function Dummy(){}
>            ^^^^^
>> function extend(proto) {
>>          Dummy.prototype=proto;
>            ^^^^^
>>          return new Dummy();
>> }

>> No closure. [...]

> I think there is one.  `Dummy' was declared in the definition
> context of `extend' that `extend' reproduces when it is called;
> that is how a closure is defined.

If you're defining closures like that, every function that calls another
function, or accesses any other global property would be a closure:

function a() { alert() }
function b() { a(); }

My informal definition is that a closure is a function that keeps
references to objects that are defined in an outer lexical scope. Dummy
here is just a property of the global object, not a lexical variable.

Joost.


 
You must Sign in before you can post messages.
To post a message you must first join this group.
Please update your nickname on the subscription settings page before posting.
You do not have the permission required to post.
Create a group - Google Groups - Google Home - Terms of Service - Privacy Policy
©2013 Google