Getting started

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


  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


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


  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


  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 "style" binding


The style binding adds or removes one or more style values to the associated DOM element. This is useful, for example, to highlight some value in red if it becomes negative, or to set the width of a bar to match a numerical value that changes.

(Note: If you don’t want to apply an explicit style value but instead want to assign a CSS class, see the css binding.)


<div data-bind="style: { color: currentProfit() < 0 ? 'red' : 'black' }">
   Profit Information

<script type="text/javascript">
    var viewModel = {
        currentProfit: ko.observable(150000) // Positive value, so initially black
    viewModel.currentProfit(-50); // Causes the DIV's contents to go red

This will set the element’s style.color property to red whenever the currentProfit value dips below zero, and to black whenever it goes above zero.


  • Main parameter

    You should pass a JavaScript object in which the property names correspond to style names, and the values correspond to the style values you wish to apply.

    You can set multiple style values at once. For example, if your view model has a property called isSevere,

    <div data-bind="style: { color: currentProfit() < 0 ? 'red' : 'black', fontWeight: isSevere() ? 'bold' : '' }">...</div>

    If your parameter references an observable value, the binding will update the styles whenever the observable value changes. If the parameter doesn’t reference an observable value, it will only set the styles once and will not update them later.

    As usual, you can use arbitrary JavaScript expressions or functions as parameter values. KO will evaluate them and use the resulting values to detemine the style values to apply.

  • Additional parameters

    • None

If you want to apply a font-weight or text-decoration style, or any other style whose name isn’t a legal JavaScript identifier (e.g., because it contains a hyphen), you must use the JavaScript name for that style. For example,

  • Don’t write { font-weight: someValue }; do write { fontWeight: someValue }
  • Don’t write { text-decoration: someValue }; do write { textDecoration: someValue }

See also: a longer list of style names and their JavaScript equivalents


None, other than the core Knockout library.