ko.plus

ko.plus is a collection of extensions to KnockoutJs that add to the core library.

Installation

Get the ko.plus package from NuGet.

Install-Package ko.plus

ko.command

ko.command creates a representation of a command that exposes isRunning, failed and other observable properties to allow binding to command state.

The created commands can be invoked directly (as you would a normal function) and as such can be bound to the click handler. They support both sychronous and asynchronous implementation code, and expose done, fail and always methods to allow continuations.

Example Implementation

function ViewModel() {
    this.doSomething = ko.command(function() {
        return $.get("...");
    })
    .done(function(data) {
        //do something with the response
    })
    .fail(function(error) {
        //handle the error
    });
}

The state properties can be bound in the UI:

<span data-bind="visible: doSomething.isRunning">Loading...</span>
<span data-bind="visible: doSomething.failed">Something went wrong!</span>

Options

action

The action function can be specified as the single parameter passed to ko.command or as the action property on an options object passed into the function.

ko.command(function() { /*...*/ });
//or
ko.command({
    action: function() { /*...*/ })
});

canExecute

An optional canExecute function can be specified to determine whether or not a command can currently be executed.

function ViewModel() {
    this.doSomething = ko.command({
        action: function() {
            return $.get("...");
        },
        canExecute: function() {
            //validation logic
            return true;
        }
    });
}

Note: the function passed as canExecute will be wrapped in a ko.computed, so if it uses other observable properties it will automatically be updated. If you need to manually inform a command that the value of canExecute has changed then you can call the canExecuteHasMutated function, which will force a reevaluation.

context

The context option sets the context in which the callbacks and action functions will be executed.

function ViewModel() {
    this.url = "...";

    this.doSomething = ko.command({
        action: function() {
            return $.get(this.url);
        },
        context: this
    });
}

Properties

isRunning

An observable that indicates whether or not the command is currently running.

canExecute

A computed observable that indicates whether or not the command is currently able to execute.

failed

An observable that indicates whether or not the last invocation of the command failed.

Functions

done

Attach a callback that will be invoked when the command completes successfully.

fail

Attach a callback that will be invoked when the command fails.

always

Attach a callback that will be invoked when the command either completes successfully or fails.

Further Reading

• Introductory Blog Post
• Updated Blog Post
• Handling Context

ko.editable & ko.editableArray

ko.editable creates an extendion of ko.observable with some additional properties to aid in beginning, cancelling and committing changes. ko.editableArray does the same for instances of ko.observableArray.

Example Implementation

function ViewModel() {
   this.value = ko.editable(123);
}

var instance = new ViewModel();
//instance.value -> 123

instance.value.beginEdit();
instance.value(456);
//instance.value -> 456

instance.value.cancelEdit();
//instance.value -> 123

Properties

isEditing

An observable property that indicates whether or not the editable is currently in edit mode.

Functions

beginEdit

Puts the editable into edit mode.

endEdit

Takes the editable out of edit mode, commiting any changes.

cancelEdit

Takes the editable out of edit mode and reverts to value at the point when beginEdit was called.

rollback

Without changing edit state, reverts back through historically committed values for this editable until it reaches the original value.

Further Reading

• Introductory Blog Post

ko.makeEditable

ko.makeEditable adds to the functionality of ko.editable and ko.editableArray (which only apply to single properties) and expands to allow object graphs to be editable.

This works by appending beginEdit, cancelEdit, endEdit and rollback methods to the target object that will visit all child properties and, if they are editable, invoke the appropriate function.

The function will be applied recursively to:

• immediate child properties that are editable (whether instances of ko.editable or other editable view models)
• any editable objects found in child arrays (either editable arrays or normal)

Example Implementation

function ViewModel() {
    this.property1 = ko.editable();
    this.property2 = ko.editable();
    this.arrayProperty = ko.editableArray([
        ko.editable(),
        ko.editable()
    ]);

    ko.makeEditable(this);
}

var instance = new ViewModel();
instance.beginEdit();

instance.property1.isEditing(); // -> true
instance.property2.isEditing(); // -> true
instance.property1.isEditing(); // -> true

Properties

isEditing

An observable property that indicates whether or not the editable is currently in edit mode.

Functions

beginEdit

Puts the editable and all child editables into edit mode.

endEdit

Takes the editable and all child editables out of edit mode, commiting any changes.

cancelEdit

Takes the editable and all child editables out of edit mode and reverts to value at the point when beginEdit was called.

rollback

Without changing edit state, reverts back through historically committed values for this editable until it reaches the original value for all child editables.

Further Reading

• Introductory Blog Post

ko.bindingHandlers.loadingWhen

The loadingWhen custom binding handler replaces the contents of a container element with a loading placeholder when the bound value is truthy.

Example Implementation

<div data-bind="loadingWhen: someAction.isRunning">
    <p>This will content will be replaced when someAction.isRunning</p>
</div>

Options

loaderClass

The loading element is automatically assigned the .loader class (defined in ko.plus.css).
The loaderClass property specifies what additional class will be assigned to the loading element that sets the loading spinner.

The default option is loader-dark (grey spinner on a transparent background), and the default ko.plus.css stylesheet contains a loader-white option (white spinner on a transparent background).

Non-default loader classes can also be assigned.

Notes

Whilst primarily designed for container elements (div, ul, etc.) the loadingWhen binding will also work with elements that directly contain text (button, a, etc.).

By default the loading spinner will overlay itself over the text in these scenarios. For a slightly better appearance, try setting a specific background colour on the element to "hide" the text content. For example, if you have a elements on a white background you could use the following:

/* CSS */
a > .loader { background-color: white; }

<!-- HTML -->
<body>
    <!-- "Click Me" will be hidden by the white background whilst command is running -->
    <a href="#" data-bind="click: command, loadingWhen: command.isRunning">Click Me</a>
</body>

Important note: don't change the background-image - this is needed to display the loading spinner.

Further Reading

• Introductory Blog post

ko.bindingHandlers.command

The command custom binding handler applies the following bindings for a ko.command instance specified through the valueAccessor:

• click bound to the command
• loadingWhen bound to command.isRunning
• enable bound to command.canExecute

Example Implementation

<button data-bind="command: someAction">Do Something</button>