Using knockout js with jquery ui sliders

Question

I'm trying to figure out if knockout js would work nicely for the following problem:

I have multiple sliders that I want to link to textboxes.

When the textbox is changed the corresponding slider must update to the new value and vice versa.

On changing the slider value or textbox a function needs to be called that uses the input from all textboxes to calculate a result.

I have my quick and dirty jQuery solution here.

Would it be easy to achieve the same result in a more elegant way using knockout js?

I guess I would need to create a custom binding handler like its done in jQuery UI datepicker change event not caught by KnockoutJS

Answer 1

Here is an example: http://jsfiddle.net/jearles/Dt7Ka/

I use a custom binding to integrate the jquery-ui slider and use Knockout to capture the inputs and calculate the net amount.

--

UI

<h2>Slider Demo</h2>

Savings: <input data-bind="value: savings, valueUpdate: 'afterkeydown'" />
<div style="margin: 10px" data-bind="slider: savings, sliderOptions: {min: 0, max: 100, range: 'min', step: 1}"></div>

Spent: <input data-bind="value: spent, valueUpdate: 'afterkeydown'" />
<div style="margin: 10px" data-bind="slider: spent, sliderOptions: {min: 0, max: 100, range: 'min', step: 1}"></div>

Net: <span data-bind="text: net"></span>

View Model

ko.bindingHandlers.slider = {
  init: function (element, valueAccessor, allBindingsAccessor) {
    var options = allBindingsAccessor().sliderOptions || {};
    $(element).slider(options);
    $(element).slider({
        "slide": function (event, ui) {
            var observable = valueAccessor();
            observable(ui.value);
        },
        "change": function (event, ui) {
            var observable = valueAccessor();
            observable(ui.value);
        }
    });
    ko.utils.domNodeDisposal.addDisposeCallback(element, function () {
        $(element).slider("destroy");
    });
  },
  update: function (element, valueAccessor) {
    var value = ko.unwrap(valueAccessor());
    if (isNaN(value)) {
        value = 0;
    }
    $(element).slider("value", value);
  }
};

var ViewModel = function() {
    var self = this;

    self.savings = ko.observable(10);
    self.spent = ko.observable(5);
    self.net = ko.computed(function() {
        return self.savings() - self.spent();
    });
}

ko.applyBindings(new ViewModel());

Answer 2

I know it's some days ago but I made a few adjustments to John Earles code:

ko.bindingHandlers.slider = {
init: function (element, valueAccessor, allBindingsAccessor) {
    var options = allBindingsAccessor().sliderOptions || {};
    $(element).slider(options);
    ko.utils.registerEventHandler(element, "slidechange", function (event, ui) {
        var observable = valueAccessor();
        observable(ui.value);
    });
    ko.utils.domNodeDisposal.addDisposeCallback(element, function () {
        $(element).slider("destroy");
    });
    ko.utils.registerEventHandler(element, "slide", function (event, ui) {
        var observable = valueAccessor();
        observable(ui.value);
    });
},
update: function (element, valueAccessor, allBindingsAccessor) {
    var value = ko.utils.unwrapObservable(valueAccessor());
    if (isNaN(value)) value = 0;
    $(element).slider("option", allBindingsAccessor().sliderOptions);
    $(element).slider("value", value);
}
};

The reason for this is that if you use options that change (fx another observable) then it won't affect the slider even if you wanted it to do so.