Ajax autocomplete (or autosuggest) with TAB completion/autofill similar to shell command line completion?

Question

I'm implementing a AJAX autocomplete/autosuggest feature, and not only do I want to do the usual show suggestions that are similar to what the user typed, but I'd like to let the user do partial completions to save typing.

So, imagine my dictionary has these values in it: "green apple", "green pear", "green fruit", "blue sky", "blue water", "blue wake".

If the user types in "g", the suggestions should be "green apple", "green pear", "green fruit", and I'd like to let the user hit TAB or something to update his query to "green ", then they could type "a" and they'd get completed to "green apple".

I'm trying to model this after linux shell command line completion.

Can you recommend a control/script that does this? Or a modification/customization of an existing control?

Answer 1

This specific type of autocompletion isn't supported in popular autocompletion plugins (for jQuery, Scripty...) because usually those provide a drop-down UI for choosing the wanted match.

So let's suppose we haven't got an out-of-the-box solution. Boo-ho. How hard can it be to code it up?

// takes a text field and an array of strings for autocompletion
function autocomplete(input, data) {
  if (input.value.length == input.selectionStart && input.value.length == input.selectionEnd) {
    var candidates = []
    // filter data to find only strings that start with existing value
    for (var i=0; i < data.length; i++) {
      if (data[i].indexOf(input.value) == 0 && data[i].length > input.value.length)
        candidates.push(data[i])
    }

    if (candidates.length > 0) {
      // some candidates for autocompletion are found
      if (candidates.length == 1) input.value = candidates[0]
      else input.value = longestInCommon(candidates, input.value.length)
      return true
    }
  }
  return false
}

// finds the longest common substring in the given data set.
// takes an array of strings and a starting index
function longestInCommon(candidates, index) {
  var i, ch, memo
  do {
    memo = null
    for (i=0; i < candidates.length; i++) {
      ch = candidates[i].charAt(index)
      if (!ch) break
      if (!memo) memo = ch
      else if (ch != memo) break
    }
  } while (i == candidates.length && ++index)

  return candidates[0].slice(0, index)
}

Test page here — it should work in normal browsers. For supporting IE use event listening from prototype.js, jQuery or other.

Answer 2

If your using jQuery, a great plugin is http://bassistance.de/jquery-plugins/jquery-plugin-autocomplete/. Simply use css to hide the dropdown box, and leave the tab-auto-complete functionality on.

I think it would be simple to make a jquery plugin for yourself...

Along the lines of Listen for the Tab Key When the tab key is pressed, trigger tab:press on input.autotab

   $(document).keydown(function(e){ if (e.keyCode = (tab-key?)){
       $('input.autotab').trigger('tab:press');
   });      

Bind input.autotab's tab:press event (in an each loop... if focus==true etc.) to either a javascript array lookup, or a xhr request, (ajax), then set that input's value as the returned data.

  $('input.autotab').bind('tab:press', function(){
      if (this.hasFocus){
         this.disabled = true;
         $.get('/autotab', { q: $(this).val() }, function(response){
               $(this).val(response);
               this.disabled = false;
         }, function(){ this.disabled = false; });
      }
  });

In your autosuggest script, write it so once the value is matched more than once in the database (use a for loop with an index, stopping at the index element where the first element is matched), and return the value up to that point.