TKO: Technical Knockout

Introduction

TKO is a two-way binding framework for creating dynamic web UIs.

Hello {{name}}!

TKO is the successor to Knockout. Compared to its predecessor, TKO features some notable improvements:

Getting Started

Here’s a full-fledged demo for ye olde TODO app:

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Migrating from Knockout

The Knockout-compatible build can be used as a drop-in replacement for existing pages that utilize Knockout. There are a few backwards-incompatible changes that may need to be addressed:

➤ Bindings can’t be multi-statement function literals

Unlike KO, because TKO doesn’t use eval for parsing bindings, only single-expression arrow functions are supported in bindings. The KO-compatible build will convert function literals in bindings into an equivalent arrow function, but only if the function body contains exactly one statement. Bindings like:


<button data-bind="click: function() { doX(); doY(); }">
  Do X then Y
</button>

…will need to have the function moved into the view model like so:


// view model
this.doXThenY = function () { doX(); doY(); }

// binding
<button data-bind="click: doXThenY">
  Do X then Y
</button>
// …or…
<button data-bind="click: () => doXThenY()">
  Do X then Y
</button>

➤ Bindings can’t access the global window scope

To limit the scope of possible XSS attacks, bindings no longer have access to the global window scope by default. Any global objects you want bindings to access should be exposed as an explicit view model property:


// before
<span data-bind="text: location.href"></span>

// after view model
this.pageUrl = window.location.href

// after binding
<span data-bind="text: pageUrl"></span>

➤ foreach with as option no longer creates child context

If you provide the as option to a foreach binding, TKO no longer creates a child binding context. This means that any uses of $parent or $parents inside of the loop will need to be updated.


// before
<ol data-bind="foreach: {data: myArray, as: 'foo'}">
  <li data-bind="text: $parent.textForFoo(foo)"></li>
</ol>

// after
<ol data-bind="foreach: {data: myArray, as: 'foo'}">
  <li data-bind="text: textForFoo(foo)"></li>
</ol>
// or
<ol data-bind="foreach: myArray">
  <li data-bind="text: $parent.textForFoo($data)"></li>
</ol>

Contributing

Bug reports, pull requests, and discussions are all welcome via the GitHub page.

Reference