filter on <dom-repeat> doesn't use JS filter syntax as specified in documentation

[David-Mulder]

The documentation states

A function that can be used to filter items out of the view. This property should either be provided as a string, indicating a method name on the element's host, or else be an actual function. The function should match the sort function passed to Array.filter. Using a filter function has no effect on the underlying items array.

First of all it should probably state callback function instead of sort function. Secondly and more importantly the calls here and here miss the index and array arguments which one would expect on Array.filter's callback function:

Function to test each element of the array. Invoked with arguments (element, index, array). Return true to keep the element, false otherwise.

Per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

And yes, this is extremely useful, as Polymer doesn't support myArray.0 bindings right now, so anytime you need to do that you have to actually use a dom-repeat just to have the binding system work '-_- (and yes, I am aware of array-selector but that would be even more confusing)

[kevinpschaaf]

Closing per Polymer/old-docs-site#1381; website documentation is updated. See discussion on #2187 for background.

[ktiedt]

When this was closed... the actual documentation in the code was not fixed.

https://github.com/Polymer/polymer/blob/master/src/lib/template/dom-repeat.html#L161-L168

[ghost]

Also here: https://github.com/Polymer/polymer/blob/master/src/lib/template/dom-repeat.html#L72-L75