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Posted 21 Aug 2003

Autocomplete edit control for Javascript

, 21 Aug 2003
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Shows how to implement a Javascript based autocomplete edit control


This is a HTML control which integrates autocomplete into the standard textbox. By adding a few lines of code, you can turn any standard textboxes into a user friendly and a rather powerful control.

How it works

Whenever the user types anything in the textbox, the onkeyup event is fired, and the script calls a function. The current text in the textbox is then compared lexically with an array of strings.

Javascript code

fruits = new Array('apple','pear','orange',
names = new Array('tom','dick','harry','john','petter','foo','bar');
function autocomplete(n,ac_array){
    if (n.value == "") return 0;
    if (event.keyCode == 8 && n.backspace){
        n.value = n.value.substr(0,n.value.length-1);
        n.backspace = false;

    var r = n.createTextRange();    
    tmp= n.value;
    if (tmp == "")return 0;
    for (z=0;z<ac_array.length;z++){
        tmp2 = ac_array[z];
        count = 0;
        for (i = 0;i<tmp.length;i++){
            if (tmp2.charAt(i) == tmp.charAt(i)){
        if (count == tmp.length){
            diff = tmp2.length - tmp.length;
            if (diff <= 0) break;
            kap = "";
            for (i=0;i<tmp2.length;i++){
                if (i >= tmp.length) kap += tmp2.charAt(i);
            n.backspace = true;
            r.text += kap;
            return 0;
    n.backspace = false;
    return 0;

<input name='fruit' type='text' class='textbox' title="Opening" 
    onkeyup="autocomplete(this,fruits)" size="20">
<input name='Name' type='text' class='textbox' title="Opening" 
    backspace='false' onkeyup="autocomplete(this,names)" size="20">

How to use the code

  1. You must define the array of strings which you want to have autocompleted.
    fruits = new Array('apple','pear','orange','mango','durain',
  2. Copy the entire autocomplete function and put it somewhere in your code.
  3. Add the event onkeyup='autocomplete(this,fruits)' in the textbox. Note that the 2nd argument should tally with the array name you defined at 1.
  4. Add the property backspace='false' in the textbox. The backspace property is applicable when a user press backspace in the textbox. It gets very irritating without the boolean; i.e. when the user press backspace, the highlighted characters get deleted, but it will automatically be replaced by the same characters due to the autocomplete.


  1. I've tested the autocomplete control with an array of size 150. The speed was pretty reasonable on my computer (P3 700Mhz). However, I'm sure the autocomplete function's string-matching algorithm can be further improved upon.
  2. Allow for case insensitive string-matching


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.

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About the Author

Singapore Singapore
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Comments and Discussions

GeneralProblem with 2 Edit Control !!! Pin
Steeve_globetrotter4-May-06 4:18
memberSteeve_globetrotter4-May-06 4:18 
GeneralRe: Problem with 2 Edit Control !!! Pin
tah siah rek ngaran naon deui18-Dec-12 8:44
membertah siah rek ngaran naon deui18-Dec-12 8:44 

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