Javascript Test

Introduction

As part of our standard recruitment procedures, we ask programming candidates to undertake a small programming exercise. This should be written in HTML/Javascript. The exercise consists of:

Part 1: writing a program to solve a problem
Part 2: writing an analysis of other solutions to the problem.

Please design and code this program alone. While you will have colleagues in your normal working environment, we need to see how good you are, not how good your current friends or colleagues are. If we hire you and your level of competence is not as indicated by this test, we will have to carefully consider whether your employment should continue past the probation period. If you do copy code from elsewhere, for any reason (e.g. a library routine), please clearly indicate its source.

You should be able to finish this exercise in 4 hours. Some of the best people can complete it in much less time, but the time that you take will depend ultimately on your skill and the amount of care you use.

All code, comments and documentation should be in English (ideally using British spelling conventions).

Submission

You should submit your complete source code and the analysis document (please note the names required for the files) in a zip file with the name AblingJavascriptTest_<your name>.zip - for example, AblingJavascriptTest_ChiMo.zip. You should email it to recruit@abling.com with the subject line "Javascript test results from <your name>".

Part 1: Programming Problem

Write a web page called wordcount.html that reads a block of text, or a file from its server, that contains ASCII encoded text and counts the occurrences of each word.

You should use standard Javascript functions, and make your code compatible with IE6 and Firefox 1.5. Do not use standard libraries that have to be installed along with your file - if necessary, copy the code that you need and insert it into your file (acknowledging the source).

The web page will have a multi-line edit box for entering the filename or block of text and a button labelled "Count words" that initiates the analysis. If a filename is entered, consisting of a single line of text which ends in ".txt" then it will request the file from the server using XMLHttpRequest (or equivalent) and analyse the file for words as outlined below. If text is entered which doesn't specify a filename, then that text will be analysed. The result of the analysis will be inserted into the web page below a heading "Results", with each word listed on a new line.

In addition, the progress of the analysis should be shown below a heading "Log" in another location in the web page. This will be a log of status messages. The status messages will be:

"Loading <filename>" (if a filename is entered)
"Analysing"
"Posting results"
"Total words: " then the total number of words found
"Unique words: " then the count of unique words
"Finished"

Each message will be prefixed with the time, in seconds (to a resolution of 1 millisecond) since the button was pressed. For example, after an analysis of "mywords.txt" the log might have these entries:

0.011 Loading mywords.txt
0.423 Analysing
0.987 Posting results
0.988 Total words: 2504
0.989 Unique words: 1254
1.254 Finished

If a filename is given, but the file is not found, a message box should be shown giving the error information, and the log entry "Not found" added to the log.

If the button is pressed again, the results (but not the log) should be cleared, and the analysis carried out according to the current contents of the edit box.

A word is a sequence of characters in the range [a-zA-Z]. Any other character is treated as a word separator.

A word may appear with mixed upper or lower case characters in the text file. Upper case characters should be converted to lower case before the word is counted.

Lines in the input file may be terminated in either the *nix style (line feed) or DOS (carriage-return, line-feed) so your program should deal sensibly with either type.

The results are to have the words listed in alphabetical order, with one word per line, followed by ": " (colon and a space) and the word count. So the word file:

Hot2hat
not/hot
nat hat-hot

would give the results:

hat: 2
hot: 3
nat: 1
not: 1

Guidelines

The guidelines below are indications of maximum size only. Your program should cope with longer words, lines and files. However, you can use this information to help you select your algorithm.

Word length:	100 characters maximum (ASCII encoding only)
Line length:	1000 characters maximum
Number of words in word list:	10,000 maximum

Layout

Please spend some time getting the web page looking neat within the constraints of a single file (no images, no external css file). Split the page into appropriate, clearly defined (e.g. by using colour and/or lines) and clearly labelled sections.

Test files

We have provided some files to help you in JSTestFiles.zip. This has two files in it:

words.txt - a sample set of words, with 63 words in total and 20 unique words.
count.txt - the expected list of words and counts from words.txt
file_server.py - a web server that is restricted to serve files from the folder it is run from. You can check the source code to confirm that there is no spyware etc in it. We provide this to help you when testing the XMLHTTPRequest aspect of your solution. If you prefer you can use another server such as Apache.

You will need to have Python installed to run file_server.py. Normally you would place a txt file, your wordcount.html file, and file_server.py in one folder. Run file_server.py, then open http://localhost/wordcount.html. Now you can enter the name of the txt file in the edit box, request it, and file_server.py will "serve" it.

Quality

Quality is paramount. You should make sure that your program is coded in a professional manner and it should be thoroughly commented throughout. While running time is important to us, we do not need you to spend a lot of time tuning and we would like to see your first correct effort. Spend more time getting it right than getting it fast. That includes carefully reviewing the requirements given here and making sure that you implement all of them.

Part 2: Analysis Document

In addition to the program, write an analysis of the algorithm you have chosen and other possible algorithms to solve the problem. Look at the expected running time of the different algorithms as a function of the number of words and the number of duplicate words. This should be no more than 4k of plain ASCII text. It should be stored in a file called analysis.txt and submitted along with your program.