Tag Archives: github

Two reasons your MarkLogic code is failing silently, part 1

If you’re new to MarkLogic application programming, it’s easy to get frustrated when your code fails without any obvious reason why.  There’s no run-time error, no exception to catch, and when you surround the code block in question with log writing expressions, the “before” log expression and the “after” log expression both work perfectly.

Even now, excellent application developers are still making these same mistakes because they’re so easy to do if you aren’t paying perfect attention.

Coworker: Hey, can you look at this code and see if you know what's wrong with it?
Me: (before he pastes the code into the IM window) 
    It's namespaces or function mapping.
Coworker: ...
Coworker: Damnit.

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Using jquery.bgpos.js with jQuery 1.8

Today, I spent way too much time working on a front-end problem to a code base that I wasn’t very familiar with.  This project’s animated navigation menu stopped working when upgrading from jQuery 1.7 to jQuery 1.8, and we needed jQuery 1.8 because of another dependency.  After digging my way through the code, I finally found that the problem was occurring because Alexander Farkas’ jquery.bgpos.js jQuery plugin was not compatible with jQuery 1.8.

Since the internals of jQuery’s animation code has changed from 1.7 to 1.8, the plugin needed to be updated as well.  I’m pasting the entirety of the change here so that, hopefully, maybe, someone else doesn’t go through the same frustration that I went through today.  I’ve made the necessary changes bold and italic in the following code block.  I can’t guarantee this code would work with jQuery versions less than 1.8 ?

 * @author Alexander Farkas
 * v. 1.02
 * Edited by Nelson Wells for jQuery 1.8 compatibility
(function($) {
        backgroundPosition: function(fx) {
            if (fx.pos === 0 && typeof fx.end == 'string') {
                var start = $.css(fx.elem,'backgroundPosition');
                start = toArray(start);
                fx.start = [start[0],start[2]];
                var end = toArray(fx.end);
                fx.end = [end[0],end[2]];
                fx.unit = [end[1],end[3]];
            var nowPosX = [];
            nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
            nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
            fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];
           function toArray(strg){
               strg = strg.replace(/left|top/g,'0px');
               strg = strg.replace(/right|bottom/g,'100%');
               strg = strg.replace(/([0-9.]+)(s|)|$)/g,"$1px$2");
               var res = strg.match(/(-?[0-9.]+)(px|%|em|pt)s(-?[0-9.]+)(px|%|em|pt)/);
               return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];

Introduction to web scraping with Node.js

The internet has a wealth of freely available information in difficult to consume formats.  For example, ClicheSite has lists of cliches, euphemisms, and other phrases that are just perfect for a hangman or Wheel of Fortune game.  Coincidentally, I wanted to write such a game to learn some new technologies, so I wrote a short, simple Node.js script to scrape some pages for those phrases.  In this tutorial, I’ll discuss how to make an HTTP request and get a page’s HTML, how to parse the HTML for specific information, and why you would and would not want to do this in the first place.
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Swap object keys and values in Javascript

There are times when I would like to do work with the values in a Javascript object used as a hash map.  For example, sometimes I’d like to iterate over the values and perform an action on them, or perhaps check that a value exists in the hash map.  In this post, I’ll write a function that inverts the keys and values in a hash map, give a couple of examples in regards to how and why you’d want to do that, and explain the short-comings of the approach.

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Introduction to memoization with Javascript

Memoization is a function optimization technique used to avoid remaking calculations in subsequent function calls.  The classic example, which we’ll demonstrate here, is the factorial function.  5! = 5 * 4 * 3 * 2 * 1… factorials are recursive in nature if we give it some thought.  5! = 5 * 4! and 4! = 4 * 3! and so on.  By recognizing this pattern, we can also recognize that if we calculate 5! and save the results, then we should not have to recalculate it when we do 7!.  Instead of calculating 7! by 7 * 6 * 5 * 4 * 3 * 2 * 1, we’ll calculate it by 7 * 6 * 5!.

We’ll first examine the naive approach and then the memoization method.  All in Javascript, and all with code samples…
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Maintain a running list of your external IP address

At home, I have a consumer level cable internet service.  I actually do not know if I have a dynamic IP address or a static IP address because I haven’t really cared enough to ask my ISP.  I would assume that I have a dynamic IP address since most ISPs charge a premium for a static IP address, but since I don’t know for sure I thought I would find out for myself.

Using http://whatismyip.com ‘s “automation” page, Perl, and cron, I am going to maintain a list of my external IP addresses.  Not only will this answer the original question, but I can also gather some additional information, such as how often my IP address changes and whether or not I can force my IP address to change by disconnecting my modem :).

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