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<h1>JavaScript binary filter</h1> |
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|
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<p> |
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<small> |
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Written by Dobrica Pavlinusic |
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<a href="http://www.rot13.org/~dpavlin/"><tt>www.rot13.org/~dpavlin</tt></a>, |
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2004-11-21 |
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</small> |
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</p> |
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|
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<p> |
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I had a real-life problem: 17000 entries which I needed to filter in |
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near-real-time to present to users just some items in unsigned list. You |
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would probably say (as I would) that this is impossible in JavaScript. |
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</p><p> |
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First naive idea was to create gigantic 17000 element JavaScript array and |
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filter through this. This took 45 minutes (no, it's not a mistake, and |
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machine is pretty decent AMD Athlon box). |
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</p><p> |
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Something has to be done. First speedup was created by splitting huge 17000 |
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element array into smaller slices (few characters) and require at least some |
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letters before displaying result. As you will soon find out, searching array |
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isn't the only problem: generating huge html (using DOM or innerHTML) can be |
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<em>very slow</em>. |
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<br/> |
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So, even if you manage to filter list fast enough, limiting filtering to |
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begin of two or three characters will dramatically reduce about of html |
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results that you have to create. |
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</p><p> |
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After initial implementation or split array, I was down from 45 minutes to |
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just 5-7 minutes which was almost 10-fold improvement. But, it was still |
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too slow for interactive use (which by old teletype standards should give |
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response to users below 3 seconds). |
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</p><p> |
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But, I had another idea at mind: why not pre-sort all segments and use fast |
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binary search? Of course, writing binary search in JavaScript isn't rocket |
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science, so approach should be valid. Buy, was I wrong. I used |
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<tt>bfilter.pl</tt> perl routine to produce my indexes. But, soon I found |
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out that sort order in JavaScript differs from browser to browser depending |
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on particular locale settings on machine. |
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</p><p> |
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While I could side-step that problem by writing localized version of sort (which |
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<a href="http://svn.rot13.org/~dpavlin/svnweb/index.cgi/js_locale/log/trunk/"> |
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I actually did</a>), this was too slow for practical use. |
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<br/> |
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So, I decided just to write <a href="combo2/translate.js">unaccent</a> |
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in JavaScript and depend that sort order of 7-bit ASCII characters is same |
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in all JavaScript implementations (current routines work for |
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<tt>ISO-8859-2</tt> encoding which is used here in Croatia and Eastern |
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Europe). |
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</p><p> |
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Response time of binary search was below 3 seconds (and decent hardware |
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again), so this <a href="bfilter.html">problem was solved</a>. But, Matko |
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sow my code and said: <em>Eh, I could write combobox using this!</em> |
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</p> |
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|
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<h1>JavaScript Combobox</h1> |
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|
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<p> |
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Implementation of combobox has a little to do with me. Other than the fact |
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that it uses <tt>bfilter</tt> described above, all the other great work is |
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done my Matko Andjelinic. He has done <a href="combo.html">initial</a> |
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implementation on which I hacked a bit, and that's why it's so ugly. |
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</p><p> |
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Matko then rewrote it in object-oriented JavaScript which produced |
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<a href="combo2/test.html">current version of combobox</a>. |
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</p><p> |
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He also did <a href="combo2/test.php">php implementation</a> |
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(which is nice if you have php application and want to create comboboxes |
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on-the-fly from database). If you want to create static index file, you can |
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use <tt>bfilter.pl</tt> script. |
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</p> |
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|
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<h1>Installation</h1> |
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|
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<p> |
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Depending on your usage (do you make static html for CD or dynamic web |
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site?) you can use bfilter and checkbox in various ways. This is a toolbox. |
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Some assembly is required to get full power of comboboxes in your web |
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application. |
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</p><p> |
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There is no demo index supplied with this distribution. To create demo index |
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file for static html examples (<tt>test.php</tt> does it for you), please |
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type: |
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<pre> |
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make combo |
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</pre> |
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on your command prompt. It will create <tt>combo-test.js</tt> with first |
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10000 entries from <tt>/usr/share/dict/words</tt>. |
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</p> |
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|
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<h1>License</h1> |
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|
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<p> |
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All code is licenced under |
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<a href="http://www.gnu.org/licenses/gpl.html">GPL</a> v2 or later. |
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</p><p> |
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More restrictive licensing (if you don't want to share your changes) is |
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available on request. |
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</p> |
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