What is the origin and purpose of the variable $data in KnockoutJS?

Question

In the KnockoutJS tutorials I stumbled upon the following code example that contains an unexplainable variable $data.

The View (html):

Answer 1

$data is part of Knockout's Binding Contexts.

Here are all the built-in variables:

• $parent
• $parents
• $root
• $component
• $data
• $index (only available within foreach bindings)
• $parentContext
• $rawData
• $componentTemplateNodes