Thanks Guys...
I actually found a script which works in virtually the same way as the
O'Reilly one, using javascript on the clientside rather than Bob's XML Data
Island solution.
I'm not sure which is the better approach, but I can guarantee the
javascript is enabled in my target browsers, so I've gone for that option.
I'm saving a few server roundtrips with no drawbacks that I can see...
My code snippet is below. In a similar vein to the O'Reilly solution, I'm
calling this procedure via the OnKeyPress event handler
Chris
Snippet:
var toFind = ""; // Variable that acts as keyboard buffer
var timeoutID = ""; // Process id for timer (used when stopping
// the timeout)
timeoutInterval = 250; // Milliseconds. Shorten to cause keyboard
// buffer to be cleared faster
var timeoutCtr = 0; // Initialization of timer count down
var timeoutCtrLimit = 3 ; // Number of times to allow timer to count
// down
var oControl = ""; // Maintains a global reference to the
// control that the user is working with.
function listbox_onkeypress(){
// This function is called when the user presses a key while focus is in
// the listbox. It maintains the keyboard buffer.
// Each time the user presses a key, the timer is restarted.
// First, stop the previous timer; this function will restart it.
window.clearInterval(timeoutID)
// Which control raised the event? We'll need to know which control to
// set the selection in.
oControl = window.event.srcElement;
var keycode = window.event.keyCode;
if(keycode >= 32 ){
// What character did the user type?
var c = String.fromCharCode(keycode);
c = c.toUpperCase();
// Convert it to uppercase so that comparisons don't fail
toFind += c ; // Add to the keyboard buffer
find(); // Search the listbox
timeoutID = window.setInterval("idle()", timeoutInterval);
// Restart the timer
}
}
function listbox_onblur(){
// This function is called when the user leaves the listbox.
window.clearInterval(timeoutID);
resetToFind();
}
function idle(){
// This function is called if the timeout expires. If this is the
// third (by default) time that the idle function has been called,
// it stops the timer and clears the keyboard buffer
timeoutCtr += 1
if(timeoutCtr > timeoutCtrLimit){
resetToFind();
timeoutCtr = 0;
window.clearInterval(timeoutID);
}
}
function resetToFind(){
toFind = ""
}
function find(){
// Walk through the select list looking for a match
var allOptions = document.all.item(oControl.id);
for (i=0; i < allOptions.length; i++){
// Gets the next item from the listbox
nextOptionText = allOptions(i).text.toUpperCase();
// By default, the values in the listbox and as entered by the
// user are strings. This causes a string comparison to be made,
// which is not correct for numbers (1 < 11 < 2).
// The following lines coerce numbers into an (internal) number
// format so that the subsequent comparison is done as a
// number (1 < 2 < 11).
if(!isNaN(nextOptionText) && !isNaN(toFind) ){
nextOptionText *= 1; // coerce into number
toFind *= 1;
}
// Does the next item match exactly what the user typed?
if(toFind == nextOptionText){
// OK, we can stop at this option. Set focus here
oControl.selectedIndex = i;
window.event.returnValue = false;
break;
}
// If the string does not match exactly, find which two entries
// it should be between.
if(i < allOptions.length-1){
// If we are not yet at the last listbox item, see if the
// search string comes between the current entry and the next
// one. If so, place the selection there.
lookAheadOptionText = allOptions(i+1).text.toUpperCase() ;
if( (toFind > nextOptionText) &&
(toFind < lookAheadOptionText) ){
oControl.selectedIndex = i+1;
window.event.cancelBubble = true;
window.event.returnValue = false;
break;
} // if
} // if
else{
// If we are at the end of the entries and the search string
// is still higher than the entries, select the last entry
if(toFind > nextOptionText){
oControl.selectedIndex = allOptions.length-1 // stick it
// at the end
window.event.cancelBubble = true;
window.event.returnValue = false;
break;
} // if
} // else
} // for
} // function
