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Auto-complete Control

, 16 May 2005
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Auto-complete control.
<!-- please do not entitify this javascript code; its for on page demo -->


Most auto-complete textboxes may have a reverse effect on end-users. Instead of helping them get things done faster, they get irritated by design flaws made by the programmer. (Admittedly, I've made such design flaws too.)

I got to learn this lesson when designing my first auto-complete edit control, found here[^]. Although it seemingly looks intuitive, I forgot to consider the fact that what if the end-user wanted to type just 'ap' but the 'ple' appears out of nowhere? This means that the end-user would then have to hunt for, and press the delete key.

After seeing how GMail made its auto-complete, I took the idea and implemented my own version of the auto-complete control.

Auto-complete textbox control:

<INPUT id=actb_textbox type=textbox>

  • Timeout: 3000ms
  • Delimiter: ; and ,
  • Options: ('an apple', 'alligator', 'elephant', 'pear', 'kingbird', 'kingbolt', 'kingcraft', 'kingcup', 'kingdom', 'kingfisher', 'kingpin')

How does it work?

The important event that will fire whenever the user press any key is onkeydown. The onkeydown event handles all the normal character input and is in charge of creating the auto-complete list. It also handles keys like 'up', 'down' and 'enter'.

Using the JavaScript regexp() object, the script will run through the array containing the keywords and match them one by one. After which, a DIV will be created dynamically using document.createElement(). Finally, when the user presses the 'Enter' key, the DIV will be detached and the input box updated.

The user can also select the options using the mouse. This is done through three events: onmouseover, onmouseout, and onclick.

How do you implement it into your own textbox?

Firstly, include the .js file into your script:

<script language="javascript" type="text/javascript" 

Next, create an array (in JavaScript) containing the keywords:

customarray = new Array('apple','pear','mango','pineapple', 
         'orange','banana','durian', 'jackfruit','etc');

Apply the widget to your textbox using JavaScript:


And you're done!


This auto-complete edit control has some customizable features:

/* ---- Variables ---- */
// Autocomplete Timeout in ms (-1: autocomplete never time out)
this.actb_timeOut = -1;
// Number of elements autocomplete can show (-1: no limit)
this.actb_lim = 4;
// should the auto complete be limited to the beginning of keyword?
this.actb_firstText = false;
// Enable Mouse Support
this.actb_mouse = true;
// Delimiter for multiple autocomplete.
// Set it to empty array for single autocomplete
this.actb_delimiter = new Array(' ',',');
// Show widget only after this number of characters is typed in.
this.actb_startcheck = 1;
/* ---- Variables ---- */

/* --- Styles --- */
this.actb_bgColor = '#888888';
this.actb_textColor = '#FFFFFF';
this.actb_hColor = '#000000';
this.actb_fFamily = 'Verdana';
this.actb_fSize = '11px';
this.actb_hStyle = 'text-decoration:underline;font-weight="bold"';
/* --- Styles --- */ 

this.actb_keywords = new Array();

The styles are pretty self-explanatory; tweak the values for best results for your own website. Firstly, the variable actb_timeOut controls how long the auto-complete list's timeout should be (i.e., after x ms, the list will disappear). By default, it is set to -1, which represents no timeout.

Next, the variable actb_lim limits the number of elements the list will show, to prevent over-spamming. If you do not want to set any limit, set it to -1.

Thirdly, the actb_firstText variable determines whether the match with the keywords-array should only start from the first character or if the match can be any arbitrary match within the keyword. For example, if firstText is set to true, then a given string "ello" will match with "hello".

Also, the actb_mouse variable determines whether the control should respond to mouse events. Mouse support works when user clicks on the auto-complete list that appears.

The actb_delimiter variable allows for the much requested multiple auto-complete feature. Set a custom delimiter, or even multiple delimiters like semi-colon (;) or comma (,), and the engine will complete words separated by the given delimiter.

Lastly, actb_startcheck controls the number of characters that must be typed in before the textbox will display the control. Thanks to flyasfly for this suggestion.


As of version 1.3, all of the above mentioned are public variables. This can be useful in emulating controls like Google Suggest. When you apply the control to your textbox using the actb function, it returns an object.

Changing the autocomplete list

obj = actb(document.getElementById('textbox_id'),customarray);
// ... after some time ...
obj.actb_keyword = new Array('this','is','a','new','set','of','keywords');

Multiple auto-complete textboxes

obj = new actb(document.getElementById('textbox_id'),customarray);
obj2 = new actb(document.getElementById('textbox2_id'),customarray2);

Multiple textboxes (different options)

obj = new actb(document.getElementById('textbox_id'),customarray);
obj.actb_mouse = false; // no mouse support
obj2 = new actb(document.getElementById('textbox2_id'),customarray2);
obj2.actb_startcheck = 2; // start actb only after 2nd character


  • Add second array (customarrayDesc) for display description in the list (ex => [an apple: it's an apple] instead of [an apple]. Suggestion by angelo77).
  • Many other features suggested by CPians, some of which might be beyond me at the moment but I'll still try my best!

Tested browsers

  • Internet Explorer 6.0.28
  • Mozilla Firefox version 1.0.3


Thank you to all of you who have supported, modified, and offered your suggestions to the control! I'm extremely apologetic for the inactiveness of this project because of schoolwork etc. However, I still try my best to work on it whenever anyone has a new feature request!


This control will be, from effect of version 1.1, published under Creative Common License [^]

Change Log

  • 1.31: 12/5/2005
    • Fix: Fixed a bug with actb_bgColor styles due to typo.
    • Fix: Now caret does not move away (Firefox) when user presses Enter or tab.
  • 1.3: 8 May 2005
    • Added: actb_startcheck has the number of characters that start the widget control. Thanks to flyasfly for suggestion.
    • Change: All 'tweakabilities' and styles have been changed to public variables.
    • Fix: Fixed an IE-specific bug which prevents the caret position of textarea to be retrieved. Now widget works for textarea too.
  • 1.2: 9 Apr 2005
    • Change: Converted the code of actb widget to OOP.
    • Fix: Mouse click bug that disallows autocomplete control from deleting itself.
    • Added: the keywords array (actb_keyword) becomes a public variable, so it can be modified from the parent script.
  • 1.1: 6 Dec 2004
    • Fix: Metacharacters escaped before parsing with RegExp.
    • Added: Multiple delimiters.
    • Added: Tab now completes the text like Enter.
    • Change: Now, only an event is needed for the control to work; the rest are attached dynamically.
    • Fix: Bugs with caret position in Firefox: originally, 'up' and 'down' keys changed caret position in the textbox for Firefox. This problem has been rectified.
  • 1.0: 23 Nov 2004
    • Fix: some miscellaneous bugs in mouse support (actb_removedisp() cannot be executed properly).
    • Fix: actb_timeout now works fine with mouse support on.
    • Added: When user moves the mouse over each individual option, the option will be highlighted.
    • Added: Multiple auto-complete! This works even if you're editing previous "fields".
  • 0.9: 6 Oct 2004
    • Fix: A bug concerning clientHeight which apparently Mozilla does not support. Thanks Cameron Smith for pointing out.
    • Added: This control now supports phrases with spaces in between. Thanks to Miguel Vieira.
    • Added: This control has mouse support. Thanks to Alecacct and everyone for the idea.
  • 18 Aug 2004
    • Basic engine created.
    • Article posted!


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author


Singapore Singapore
I'm young and cool Smile | :)

Comments and Discussions

GeneralThanks for the code Pinmemberbasheerpt1-Sep-09 0:12 
GeneralMinor error PinmemberGeorge Farnsworth20-Aug-09 12:10 
QuestionHow to use it in ASP.Net 2.0 Pinmemberhon1234566-Aug-09 0:43 
AnswerRe: How to use it in ASP.Net 2.0 Pinmemberarpizt3-May-10 17:22 
GeneralNice function but difficult to read. Pinmemberalwyn224-Jul-09 1:53 
GeneralLike it but hard to read Pinmemberr3kb6-Jul-09 22:11 
I like the control quite a bit, but I find that the code it's based on is difficult to read. I would hope that a choice would be made to change to code that self-documents more. Over time, I've learned that commenting every line of code is more distracting than helpful. Code that self-documents uses variable and method names that describe what each is used for. IMNSHO, comments are best used to describe intent, nuances, and challenges. Single letter variables are okay for counters in loops, but it's easier to see what the counter is used for if it's descriptive...

Thanks for the tool and the article. I find it useful already, but I can see that in order to incorporate it into what I'm doing, I'll need to make some changes to it.
Cool | :cool:
GeneralAwesome! PinmemberKdiggins29-Jun-09 16:02 
QuestionAutocomplete+dynamically Pinmemberkamaraju.prathi24-Jun-09 5:05 
AnswerRe: Autocomplete+dynamically [modified] PinmemberKlaaslievens4-Jul-09 0:17 
GeneralCan't align to left Pinmembermark39606-Jun-09 8:38 
GeneralCross-Browser PinmemberTale Masinov28-May-09 4:59 
GeneralUpdated control and support [modified] PinmemberDmitry Khudorozhkov15-Apr-09 18:02 
Generalassociate ID with the array Pinmemberrzshiplu30-Mar-09 21:40 
Generalnot properly working ie 5 Pinmemberuraj0830-Mar-09 19:29 
GeneralMouse event does not work PinmemberMember 22452888-Mar-09 22:21 
GeneralSimple update for associative arrays Pinmemberstriderman26-Feb-09 10:02 
QuestionPg up and display list PinmemberBenRyder9-Feb-09 4:59 
GeneralEnhanced Pinmemberjfsanchez2k1-Feb-09 7:10 
GeneralAbsolutely flawlessly Pinmemberevilrafael28-Jan-09 7:54 
GeneralI need your help Pinmemberhwlp21-Jan-09 2:50 
GeneralProblems with div tags PinmemberChrLange15-Jan-09 2:40 
GeneralRe: Problems with div tags PinmemberChrLange15-Jan-09 4:25 
Generalshowing the same array of keywords for two different text boxes Pinmembervelm12311-Jan-09 21:10 
AnswerRe: showing the same array of keywords for two different text boxes PinmemberBrad Kirby3-Mar-09 12:08 
GeneralRe: showing the same array of keywords for two different text boxes Pinmembermandelbrot197023-Sep-09 1:57 
QuestionSearch multiple parts of an item? Pinmemberharoldsaxon10-Jan-09 3:05 
GeneralThank you! Pinmemberndkha130-Dec-08 11:26 
GeneralScripts interfering with seperate form validation PinmemberConcoxide3-Dec-08 11:12 
General1st Item Focus PinmemberMember 190445012-Nov-08 7:05 
GeneralRe: 1st Item Focus PinmemberMember 190445019-Nov-08 5:31 
GeneralRe: 1st Item Focus - SOLVED [modified] PinmemberConcoxide3-Dec-08 9:41 
GeneralJavaScript Warning PinmemberMember 190445012-Nov-08 2:24 
GeneralRe: JavaScript Warning PinmemberMember 190445012-Nov-08 2:31 
GeneralExcelente Trabajo Pinmemberjorgetinito11-Nov-08 9:27 
GeneralGood Idea PinmemberAmir Raoof5-Nov-08 9:57 
Generalactb_lim isn't respected Pinmemberzqfhpzxuckr2-Nov-08 2:07 
Generalautocomplete textbox Pinmemberzius07530-Oct-08 22:28 
GeneralMatch First Characters of Any Word - (Not any part of the string) Pinmembercascharly10-Oct-08 3:58 
GeneralRe: Match First Characters of Any Word - (Not any part of the string) - SOLVED PinmemberConcoxide3-Dec-08 6:37 
QuestionMy autocomplete list only ever shows 1 option Pinmemberoxfordmonty031010-Oct-08 2:47 
GeneralNeed to populate the list Array from a MySql Query - Help Needed Pinmembercascharly8-Oct-08 9:34 
GeneralRe: Need to populate the list Array from a MySql Query - Help Needed Pinmemberoxfordmonty031010-Oct-08 2:20 
GeneralRe: Need to populate the list Array from a MySql Query - Help Needed [modified] - - SOLVED HERE Pinmembercascharly10-Oct-08 3:40 
GeneralRe: Need to populate the list Array from a MySql Query - Help Needed [modified] - - SOLVED HERE Pinmemberkiran Gabhane30-Sep-10 6:22 
Questioncan we pass two dimensional array in it?? PinmemberJagwinder Walia26-Sep-08 1:58 
AnswerRe: can we pass two dimensional array in it?? Pinmemberevilrafael28-Jan-09 7:59 
General2 Dimensional Array PinmemberSBrow17-Sep-08 3:00 
GeneralRe: 2 Dimensional Array PinmemberJagwinder Walia26-Sep-08 20:51 
QuestionChange font color black to white when moving over the list Pinmemberashrithos9-Sep-08 7:18 
GeneralExcellent Pinmemberasilkumar5-Sep-08 0:36 

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