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Auto-complete Control

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4.87 (189 votes)
16 May 2005
Auto-complete control.


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:

  • 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

AnswerRe: auto-complete for textareas? Pin
dharmanands24-May-05 21:59
Memberdharmanands24-May-05 21:59 
GeneralERROR Pin
mizzar14-Apr-05 4:30
Membermizzar14-Apr-05 4:30 
GeneralRe: ERROR Pin
Anonymous19-Apr-05 13:00
MemberAnonymous19-Apr-05 13:00 
GeneralShow Popuplist through function call Pin
T.Haberkern14-Apr-05 1:49
MemberT.Haberkern14-Apr-05 1:49 
GeneralRe: Show Popuplist through function call Pin
stilpu4-May-05 0:16
Memberstilpu4-May-05 0:16 
Generalupdating array dynamically Pin
jitdsm8-Apr-05 5:20
Memberjitdsm8-Apr-05 5:20 
GeneralRe: updating array dynamically Pin
zichun14-Apr-05 2:24
Memberzichun14-Apr-05 2:24 
GeneralRe: updating array dynamically Pin
jitdsm14-Apr-05 3:57
Memberjitdsm14-Apr-05 3:57 
GeneralRe: updating array dynamically Pin
mkhines3-May-05 6:03
Membermkhines3-May-05 6:03 
GeneralArray from SQL Query Pin
mkhines4-May-05 2:26
Membermkhines4-May-05 2:26 
Questionanyone help me with this tweak? Pin
akarchm0130-Mar-05 9:20
sussakarchm0130-Mar-05 9:20 
GeneralOne more thing Pin
Member 17713391-Mar-05 14:25
MemberMember 17713391-Mar-05 14:25 
GeneralSafari Support Pin
ubergraham26-Feb-05 15:01
Memberubergraham26-Feb-05 15:01 
GeneralTabbing around forms Pin
mattcodermonkey9-Feb-05 11:24
Membermattcodermonkey9-Feb-05 11:24 
GeneralRe: Tabbing around forms Pin
gozaru17-Feb-05 23:26
Membergozaru17-Feb-05 23:26 
GeneralRe: Tabbing around forms Pin
DeFirmo22-Feb-05 14:10
MemberDeFirmo22-Feb-05 14:10 
GeneralIE autocomplete displays over custom auto-complete Pin
TechKid15-Jan-05 2:36
MemberTechKid15-Jan-05 2:36 
GeneralRe: IE autocomplete displays over custom auto-complete Pin
illig17-Jan-05 4:13
Memberillig17-Jan-05 4:13 
GeneralRe: IE autocomplete displays over custom auto-complete Pin
Anonymous13-Feb-05 16:17
MemberAnonymous13-Feb-05 16:17 
GeneralHighlight items not found in list Pin
tunnelhustler12-Jan-05 10:58
Membertunnelhustler12-Jan-05 10:58 
QuestionHow to view whole list? Pin
illig10-Jan-05 6:15
Memberillig10-Jan-05 6:15 
AnswerRe: How to view whole list? Pin
illig19-Jan-05 4:23
Memberillig19-Jan-05 4:23 
GeneralAnother auto-complete box Pin
dfrankow8-Jan-05 6:26
Memberdfrankow8-Jan-05 6:26 
QuestionHow to return the index (in the array) of the custarray! Pin
Anonymous7-Jan-05 23:02
MemberAnonymous7-Jan-05 23:02 
AnswerRe: How to return the index (in the array) of the custarray! Pin
zichun8-Jan-05 2:14
Memberzichun8-Jan-05 2:14 

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Posted 17 Aug 2004


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