Data-bind: {foreach: …} for multiple arrays

Question

Is it possible to use data-bind: foreach for more than one array?
For example:

<div data-bind="foreach: arrayone, arraytwo">
   //do stuff
</div>

If it's possible, what is the correct syntax for it ? Or what is the correct way of doing this (besides merging the two arrays) ?

Answer 1

I don't think there is any official way of doing so, but a workaround would be, to use $index along with foreach on the longer array. Something like this:

var model = function() {
  var self = this;
  
  self.arr1 = ko.observableArray([1,2,3, 5, 6]);
  self.arr2 = ko.observableArray([1,2,3,4]);
  
}

ko.applyBindings(new model());

span {
  font-weight: bold;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<br/>

<div data-bind="foreach: (arr1().length > arr2().length ? arr1 : arr2)">
  Index: 
  <span data-bind="text: $index"></span>,
  
  Array 1: 
  <span data-bind="text: $root.arr1()[$index()]"></span>,
  Array 2: 
  <span data-bind="text: $root.arr2()[$index()]"></span>,
  Longer array: 
  <span data-bind="text: $data"></span>,
  Shorter array: 
  <span data-bind="text: ($root.arr1().length < $root.arr2().length ? $root.arr1()[$index()] : $root.arr2()[$index()])"></span>
  <br/>
</div>