I was reading a blog post the other day (sorry, lost the URL...), it gives a pretty cool optimization in for loop;

In stead of:

for ($i < 0; $i < count($array_X); $i++) {

  // do something....

}

One can do this and only one count() is executed:

for ($i < 0, $cnt = count($array_X); $i < $cnt; $i++) {

  // do something....

}

I alright has a little concern when I put in that count(), or whatever expensive operation in the evaluation. But never think of this trick, even I know about I can initialize more than one value in a loop.

My home network always has local domain setup so I can ssh to admun2 instead of 192.168.0.x.

This is achieved by running a bind server w/ DNS forwarding, and a local domain served by bind. This works and provide a mean for me to learn about setting DNS domain in a small network.

But this time around when I move my server setup to CentOS 5, I read about dnsmasq. After some research, it seems this provides the function I setup w/ bind, but much easier to configure!

1) install (or ensure) dnsmasq: yum install dnsmasq
2) start the server: /etc/init.d/dnsmasq start
3) setup server to start on boot-up: chkconfig --level 345 dnsmasq on
4) ensure DNS port (TCP port 53) is unblocked in the firewall
5) setup /etc/hosts with local domain IP/hostname i.e. 192.168.0.99 admun2
6) set dnsmasq server IP as primary DNS in DSL router's DHCP setting

I never really done much of math in shell script in the past, but a script that collect logs recently require some simple add up.

#!/bin/sh

x=1;

y=2;

echo $((x+y));

It's cool to able to chain more than one action together:

$('#myTable')  

    .find('.firstColumn')  

        .css('background','red')  

    .end()  

    .find('.lastColumn')  

        .css('background','blue');

Meanwhile, one can make a chainable function with this:

$.fn.mySetVal = function(x,y) {  

    return $(this).val(x,y);  

}

I don't think there is a easier way to do it:

$ampm_time = date("g:i A", strtotime($24hr_time));

To compare 2 dates in javascript actually pretty easy:

var timeFrom = new Date(from);

var timeTo = new Date(to);

if (timeFrom - timeTo > 0) {

  // do something if a date range is invalid

}

I was recently searching on-line for how to do URL validation in Javascript. The best one I found so far is this:

  url = 'http://somewhere.com';

  var rx = new RegExp();

  rx.compile(/http:\/\/[A-Za-z0-9\.-]{3,}\.[A-Za-z]{3}/);

  if (rx.test(url)) {

    doSomethingForURL();

  }

Question of the day at work: How can I tell id a selector find something, or a particular DOM element exists?

It turns out that $() always return a object, which has a .length can be used to see if something has found.

So, I can do something like:

if ($('something').length > 0) {

  alert('The DOM element has found!');

}

There is one more way to archive the same:

if ($('something').is('*') != '') {

  alert('The DOM element has found!');

}