knockout autocomplete

fiddle.html

<input data-bind="jqAuto: { autoFocus: true }, jqAutoSource: myPeople, jqAutoValue: mySelectedGuid, jqAutoSourceLabel: 'displayName', jqAutoSourceInputValue: 'name', jqAutoSourceValue: 'guid'" />

<hr/>


<div data-bind="text: mySelectedGuid() ? mySelectedGuid() : 'None selected'"></div>

<hr/>

For testing setting the model value elsewhere:
<select data-bind="options: myPeople, optionsCaption: 'select a person...', optionsText: 'displayName', optionsValue: 'guid', value: mySelectedGuid"></select>

<hr/>

fiddle.js

//jqAuto -- main binding (should contain additional options to pass to autocomplete)
//jqAutoSource -- the array of choices
//jqAutoValue -- where to write the selected value
//jqAutoSourceLabel -- the property that should be displayed in the possible choices
//jqAutoSourceInputValue -- the property that should be displayed in the input box
//jqAutoSourceValue -- the property to use for the value
ko.bindingHandlers.jqAuto = {
    init: function(element, valueAccessor, allBindingsAccessor, viewModel) {
        var options = valueAccessor() || {},
            allBindings = allBindingsAccessor(),
            unwrap = ko.utils.unwrapObservable,
            modelValue = allBindings.jqAutoValue,
            source = unwrap(allBindings.jqAutoSource),
            valueProp = allBindings.jqAutoSourceValue,
            inputValueProp = allBindings.jqAutoSourceInputValue || valueProp,
            labelProp = allBindings.jqAutoSourceLabel || inputValueProp;

        //function that is shared by both select and change event handlers
        function writeValueToModel(valueToWrite) {
            if (ko.isWriteableObservable(modelValue)) {
               modelValue(valueToWrite );  
            } else {  //write to non-observable
               if (allBindings['_ko_property_writers'] && allBindings['_ko_property_writers']['jqAutoValue'])
                        allBindings['_ko_property_writers']['jqAutoValue'](valueToWrite );    
            }
        }
        
        //on a selection write the proper value to the model
        options.select = function(event, ui) {
            writeValueToModel(ui.item ? ui.item.actualValue : null);
        };
            
        //on a change, make sure that it is a valid value or clear out the model value
        options.change = function(event, ui) {
            var currentValue = $(element).val();
            var matchingItem =  ko.utils.arrayFirst(source, function(item) {
               return unwrap(item[inputValueProp]) === currentValue;  
            });
            
            if (!matchingItem) {
               writeValueToModel(null);
            }    
        }
        
        
        //handle the choices being updated in a DO, to decouple value updates from source (options) updates
        var mappedSource = ko.dependentObservable(function() {
                mapped = ko.utils.arrayMap(source, function(item) {
                    var result = {};
                    result.label = labelProp ? unwrap(item[labelProp]) : unwrap(item).toString();  //show in pop-up choices
                    result.value = inputValueProp ? unwrap(item[inputValueProp]) : unwrap(item).toString();  //show in input box
                    result.actualValue = valueProp ? unwrap(item[valueProp]) : item;  //store in model
                    return result;
            });
            return mapped;                
        });
        
        //whenever the items that make up the source are updated, make sure that autocomplete knows it
        mappedSource.subscribe(function(newValue) {
           $(element).autocomplete("option", "source", newValue);
        });
        
        options.source = mappedSource();
        
        //initialize autocomplete
        $(element).autocomplete(options);
    },
    update: function(element, valueAccessor, allBindingsAccessor, viewModel) {
       //update value based on a model change
       var allBindings = allBindingsAccessor(),
           unwrap = ko.utils.unwrapObservable,
           modelValue = unwrap(allBindings.jqAutoValue),
           valueProp = allBindings.jqAutoSourceValue,
           inputValueProp = allBindings.jqAutoSourceInputValue || valueProp;
        
       //if we are writing a different property to the input than we are writing to the model, then locate the object
       if (valueProp && inputValueProp !== valueProp) {
           var source = unwrap(allBindings.jqAutoSource) || [];
           var modelValue = ko.utils.arrayFirst(source, function(item) {
                 return unwrap(item[valueProp]) === modelValue;
           }) || {};             
       }

       //update the element with the value that should be shown in the input
       $(element).val(modelValue && inputValueProp !== valueProp ? unwrap(modelValue[inputValueProp]) : modelValue.toString());    
    }
};

function Person(guid, name, email) {
    this.guid = ko.observable(guid);
    this.name = ko.observable(name);
    this.email = ko.observable(email);
    
    this.displayName = ko.dependentObservable(function() {
        return this.name() + " [" + this.email() + "]";
    }, this);
}

var viewModel = {
    myPeople: ko.observableArray([
        new Person("5658ff20-f230-4176-97d1-0ac21abfdbdf", "Bob Smith", "bsmith@company.com"),
        new Person("1d7b9b28-25b7-40de-bec1-0a5426228f5b", "Bonnie Johnson", "bjohnson@company.com"),
        new Person("28605d66-d794-4a09-8452-0278abd690c6", "John Daniels", "jdaniels@company.com"),
        new Person("7c4881ef-5530-45c9-96eb-5dceed6cd4c9", "Deborah Danielson", "ddanielson@company.com"),
        new Person("ec361d63-38ae-4ecc-ab46-6c0ef19ed3ac", "John Daniels", "jxdaniels@company.com")
    ]),
    mySelectedGuid: ko.observable("ec361d63-38ae-4ecc-ab46-6c0ef19ed3ac")
};

ko.applyBindings(viewModel);

fiddle.manifest

name: jQuery UI autocomplete - original rniemeyer version
description: knockout autocomplete, see https://groups.google.com/d/topic/knockoutjs/ABhEeI7jLKA/discussion
authors:
  - rniemeyer
resources:
  - jsfiddle-defaults.user.js
  - http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.14/themes/base/jquery-ui.css
  - http://rniemeyer.github.com/KnockMeOut/Scripts/jquery.tmpl.js
  - http://rniemeyer.github.com/KnockMeOut/Scripts/knockout-latest.debug.js
normalize_css: no

jsfiddle-defaults.user.js

// ==UserScript==
// @name Sensible defaults for jsFiddle.
// @author Mathias Bynens <http://mathiasbynens.be/>
// @link http://mths.be/bde
// @match http://jsfiddle.net/*
// ==/UserScript==

// Insert JS before </body> and don’t use any libraries by default
[].forEach.call(document.querySelectorAll('#js_wrap option[value="b"], #js_lib option[value="11"]'), function(el) {
el.selected = true;
});

// Don’t use the “normalized” CSS (it’s more like a reset anyway)
document.getElementById('id_normalize_css').checked = false;