why use the "!!!"?

Posted by lazyanno on Stack Overflow See other posts from Stack Overflow or by lazyanno
Published on 2010-06-11T04:15:42Z Indexed on 2010/06/11 4:22 UTC
Read the original article Hit count: 169

Filed under:

JavaScript

|

Performance

|

data-structures

as follow codes:

var a = {};
if(!!!a[tabType]){
   a[tabType] = [];
   a[tabType].push([self,boxObj]);
}else{
   a[tabType].push([self,boxObj]);
}

i think !!!a[tabType] equals !a[tabType] why use the "!!!" not "!" ?

thank you!

© Stack Overflow or respective owner

Related posts about JavaScript

CHAT ROOMs 7 by 6

as seen on Stack Overflow - Search for 'Stack Overflow'
I am looking for chatroom on one page with 7 loggedin users and 6+rows for say 42 users.these users will keep on adding wthnew users.Need urgent help.A PRETTY UNUSUAL Q FOR MOST OF U.What is MORE REQ new features: Usernames are unique to users currently chatting You can see a "currently chatting"… >>> More
Integrating JavaScript Unit Tests with Visual Studio

as seen on Stephen Walter - Search for 'Stephen Walter'
Modern ASP.NET web applications take full advantage of client-side JavaScript to provide better interactivity and responsiveness. If you are building an ASP.NET application in the right way, you quickly end up with lots and lots of JavaScript code. When writing server code, you should be writing… >>> More
Has Javascript developed beyond what it was originally designed to do?

as seen on Programmers - Search for 'Programmers'
I've been talking with a friend about the purpose of Javascript, when and how it should be used, etc. He quoted that: JavaScript was designed to add interactivity to HTML pages [...] JavaScript gives HTML designers a programming tool HTML authors are normally not programmers… >>> More
PHP, javascript, single quote problems with IE when passing variable from ajax post to javascript fu

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi! I have been trying to get this to work for a while, and I suspect there's an easy solution that I just can't find. My head feels like jelly and I would really appreciate any help. My main page.php makes a .post() to backend.php and fetches a list of cities which it echoes in the form of: <li… >>> More
Javascript in XSL that is loaded by Javascript

as seen on Stack Overflow - Search for 'Stack Overflow'
Is there anyway to have javascript run when a XSL sheet has been applied to an XML file by Javascript? I am using a JQuery plugin to apply the sheet to the xml but the javascript that is located inside of the XSL file will not run. I put the Javascript at the bottom of the file and it still does… >>> More

Related posts about Performance

Improving VPN performance - stronger encryption = more performance?

as seen on Server Fault - Search for 'Server Fault'
I have a site-to-site VPN set up with two SonicWall's (a TZ170 and a Pro1260). It was suggested to me that turning off encryption (so the VPN is tunneling only) would improve performance. (I'm not concerned with security, because the VPN is running over a trusted line.) Using FTP and HTTP transfers… >>> More
Inaccurate performance counter timer values in Windows Performance Monitor

as seen on Stack Overflow - Search for 'Stack Overflow'
I am implementing instrumentation within an application and have encountered an issue where the value that is displayed in Windows Performance Monitor from a PerformanceCounter is incongruent with the value that is recorded. I am using a Stopwatch to record the duration of a method execution, then… >>> More
Excel-based Performance Reviews transformed into Web Application for Performance Management

as seen on Geeks with Blogs - Search for 'Geeks with Blogs'
HR TMS provides enterprise talent management solutions for healthcare, retail and corporate customers, focusing on performance management, compensation management and succession planning. As the competency of nurses and other healthcare workers is critical, the government, via the Joint Commission… >>> More
How to save a perfmon Performance Counter as a textfile (Reliability and Performance Monitor Version

as seen on Server Fault - Search for 'Server Fault'
Now the file gets saved as blg, but I would like a txt versin to import in Excel. >>> More
SQLAuthority News – A Successful Performance Tuning Seminar at Pune – Dec 4-5, 2010

as seen on SQL Authority - Search for 'SQL Authority'
This is report to my third of very successful seminar event on SQL Server Performance Tuning. SQL Server Performance Tuning Seminar in Colombo was oversubscribed with total of 35 attendees. You can read the details over here SQLAuthority News – SQL Server Performance Optimizations Seminar – Grand… >>> More