Getting started

  1. How KO works and what benefits it brings
  2. Downloading and installing

Observables

  1. Creating view models with observables
  2. Working with observable arrays

Computed observables

  1. Using computed observables
  2. Writable computed observables
  3. How dependency tracking works
  4. Pure computed observables
  5. Reference

Bindings

Controlling text and appearance

  1. The visible binding
  2. The text binding
  3. The html binding
  4. The css binding
  5. The style binding
  6. The attr binding

Control flow

  1. The foreach binding
  2. The if binding
  3. The ifnot binding
  4. The with binding
  5. The component binding

Working with form fields

  1. The click binding
  2. The event binding
  3. The submit binding
  4. The enable binding
  5. The disable binding
  6. The value binding
  7. The textInput binding
  8. The hasFocus binding
  9. The checked binding
  10. The options binding
  11. The selectedOptions binding
  12. The uniqueName binding

Rendering templates

  1. The template binding

Binding syntax

  1. The data-bind syntax
  2. The binding context

Creating custom bindings

  1. Creating custom bindings
  2. Controlling descendant bindings
  3. Supporting virtual elements
  4. Custom disposal logic
  5. Preprocessing: Extending the binding syntax

Components

  1. Overview: What components and custom elements offer
  2. Defining and registering components
  3. The component binding
  4. Using custom elements
  5. Advanced: Custom component loaders

Further techniques

  1. Loading and saving JSON data
  2. Extending observables
  3. Deferred updates
  4. Rate-limiting observables
  5. Unobtrusive event handling
  6. Using fn to add custom functions
  7. Microtasks
  8. Asynchronous error handling

Plugins

  1. The mapping plugin

More information

  1. Browser support
  2. Getting help
  3. Links to tutorials & examples
  4. Usage with AMD using RequireJs (Asynchronous Module Definition)

The "enable" binding

Purpose

The enable binding causes the associated DOM element to be enabled only when the parameter value is true. This is useful with form elements like input, select, and textarea.

Example

<p>
    <input type='checkbox' data-bind="checked: hasCellphone" />
    I have a cellphone
</p>
<p>
    Your cellphone number:
    <input type='text' data-bind="value: cellphoneNumber, enable: hasCellphone" />
</p>

<script type="text/javascript">
    var viewModel = {
        hasCellphone : ko.observable(false),
        cellphoneNumber: ""
    };
</script>

In this example, the 鈥淵our cellphone number鈥 text box will initially be disabled. It will be enabled only when the user checks the box labelled 鈥淚 have a cellphone鈥.

Parameters

  • Main parameter

    A value that controls whether or not the associated DOM element should be enabled.

    Non-boolean values are interpreted loosely as boolean. For example, 0 and null are treated as false, whereas 21 and non-null objects are treated as true.

    If your parameter references an observable value, the binding will update the enabled/disabled state whenever the observable value changes. If the parameter doesn鈥檛 reference an observable value, it will only set the state once and will not do so again later.

  • Additional parameters

    • None

Note: Using arbitrary JavaScript expressions

You鈥檙e not limited to referencing variables - you can reference arbitrary expressions to control an element鈥檚 enabledness. For example,

<button data-bind="enable: parseAreaCode(viewModel.cellphoneNumber()) != '555'">
    Do something
</button>

Dependencies

None, other than the core Knockout library.

(c) knockoutjs.com