Last night I met Jennifer again and apart from being hot it turns out she's pretty perceptive as well. When she read my previous article, she objected to some aspects of my address book.

Her point is, it's a waste of memory to store empty properties of an address. That's true, so I sat down and threw away those unneccessary bits:

Unfortunately, we now encounter some problems: First checking for an empty string no longer is sufficent, and second, since undefined is not a string, concatenating is a problem:

This is about three women and a javascript address book. The first woman is my mom. Though she does have a first name and a last name, I have been referring to her as mom for my whole life, so her entry in my address book should be labelled "Mom".

The second woman is my probation officer, a Mrs. Mathilda Wozzle. I do not have a nickname for her, and obviously I don't want anybody who happens to look over my shoulder to see what she is. Her address book entry should therefore be labelled innocently "Mathilda Wozzle".

The third woman is Jennifer. I met her in a pub last week, and I do not remember her last name. I'm not even sure she gave me a last name, can't remember much of that night. The note she handed me contained only two bits, Jennifer and a phone number. I definitely want her in my address book and until further contact she has to go as "Jennifer".

I'm afraid it's getting technical now.

My address book now looks like this:

 Read more

This article will describe how to build a more complex javascript application. I chose to build a number cruncher for finding sociable numbers. There are many idle browser out there and the new Worker-thread object (available in modern browsers) offers the complete power of all cpu cores. In the first part I will describe how to inherit javascript objects with the optimization steps and discuss the usage of a profiler. The second part will improve the performance with using Web Worker in threads for greater computing power and how to handle it.

introduction

Did you heard of perfect numbers? No? A number is perfect if the number is equal to the sum all proper positive divisors. The old greek mathematics found the following examples (or try out the demo):

The 6 has as positive divisors 1, 2 and 3 and the sum is 6.Read more

After the fine and long article about escaping from Matthias here some examples for special characters in a simple web application. This article should be only an inspiration, I will describe some code samples with python/javascript and explain why [<"@%'&_\?/:;,>কী €] is the ultimate input to test input in web applications.

The demo application offers a simple form with name and message field for an one-line guest book.Read more

The German lottery currently holds a jackpot of about 30 million Euro. A friend of mine took the bait and participated yesterday. Since he is a software developer, he wrote a small program to get him six random numbers in the range of 1 and 49.

Well, it's not difficult to write such a programm. The challenge is to do so in little bytes. So I challenge you:

Write a JavaScript function that generates random lotto numbers. This function has to return an array of six different numbers from 1 to 49 (including both) in ascending order. You may use features of ECMA-262 only, that means no Array.contains and stuff. You must not induce global variables.

The function has to look like this

Finding an IP address in text or string with python is a simpler task than in java. Only the regex is not shorter than in the java regex example!

First an example with python: build a RegExp-Object for faster matching and than loop over the result iterator.

A regex like /\d+\.\d+\.\d+\.\d+/ wont work, because there match "999.999.111.000" too. But for the usage in python - that is it! Using a regular expression is more native in python than in java. Or in javascript or in perl or asp.net... Read more

Javascript is a weird language. Great but weird. Take functions for example. You cannot only pass any type of arguments, you can also pass any number of arguments. This may be quite disturbing, especially for Java developers. Recently I had a discussion with a Java developer who complained about missing code assistance in Javascript, by which he meant no hint about the type of an argument.

This is of course due to the dynamically typed nature of Javascript. While in Java you denote the expected type of a parameter, and it's the caller's duty to pass the correct type (even more, you cannot pass a different type), in Javascript it's the function's duty to handle the given parameters and do something reasonable with unexpected types. The question arises: How do you write type safe functions in Javascript? Let me explain this by an example implementation to calculate the greatest common divisor of two numbers.Read more

In this part I will introduce the python implementation of the ip to geolocation script. It's more object oriented and hopefully better to read. In the first part of this article I willdescribe the solution to read http resources and parse the content. The second part is the same like the php version. As conclusion I will compare the results of all five APIs with the data from the cache.Read more

• the tutorial how to use ip to geolocation provider api
• the free usage ip to geolocation aggregator script
• the php stand alone implementation
• the python google appengine implementation

This is the fourth (and last) part of a series "All about types" in Javascript.

1. The basics - types and general rules of conversion
2. Automatic type conversion
3. Explicit type conversion
4. Type detection

The drawback of having a loosely typed language like Javascript, is that you sometimes have to determine the current type of a variable. This mostly occurs when you create a function that accepts different types of parameters - or is limited to one type.Read more

If you provide a restaurant guide it would be great to show the next restaurant based on webpage visitors position or the local beer garden specials if its sunny weather? Or offer geo targeted ads on your page? And this could be offered without registration or connection to a social network? I will describe the api/implementation details and offer directly our free "ip to geolocation aggregator"-script.

The first step is determining geo location based on Internet IP address of the visitor. I have found five free service providers which offer data based on the client-IP the geo position and city/country data. Classic "ip to geolocation data offers" are commercial. You have to buy and download a sql dump or csv file with ip ranges from isp with country and city data - some expanded with long/lat values. The second solution (and to save hosting space) is using a http api which offer theses data directly when being called - these looks like the preferred possibility. And the third way is to include a javascript which can integrate the geo position directly without need of a server component.Read more