Knockout search in observable array

I try to search by name in observable array. Here's my code:

<input class="form-control" data-bind="value: Query, valueUpdate: 'keyup'" autocomplete="off">

And my code in ViewModel

viewModel.Query = ko.observable('');

viewModel.search =  function(value) {
    viewModel.TestList.removeAll();
    for (var x in viewModel.TestList) {
        if (viewModel.TestList[x].Name.toLowerCase().indexOf(value.toLowerCase()) >= 0) {
            viewModel.TestList.push(viewModel.TestList[x]);
        }
    }
}
viewModel.Query.subscribe(viewModel.search);

First: I would like to search by name string. Two: Is there any other sollutions to not remove all elements from the view? I mean when query string is empty, there should be all list again.

Now I have error message:

TypeError: viewModel.TestList[x].Name is undefined

Solution

Use a computed observable array to show search results, along these lines:

var viewModel = {
  items: [ { Name: "Apple part" }, { Name: "Apple sauce" }, { Name: "Apple juice" }, { Name: "Pear juice" }, { Name: "Pear mush" }, { Name: "Something different" } ]
};

viewModel.Query = ko.observable('');

viewModel.searchResults = ko.computed(function() {
    var q = viewModel.Query();
    return viewModel.items.filter(function(i) {
      return i.Name.toLowerCase().indexOf(q) >= 0;
    });
});

ko.applyBindings(viewModel);

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>

<input class="form-control" data-bind="value: Query, valueUpdate: 'keyup'" autocomplete="off">

<h3>Search results:</h3>
<ul data-bind="foreach: searchResults">
  <li data-bind="text: Name"></li>
</ul>

<h3>All items:</h3>
<ul data-bind="foreach: items">
  <li data-bind="text: Name"></li>
</ul>

This also removes the need for a subscription or seperate function.

This example utilizes:

A regular observableArray for storing all items (this list is always the same, regardless of your search query);
A read-only computed observable which returns a filtered array of items that match your query;
The array filter method (you call it on the observableArray, but KO just forwards it to the underlying array);

As you can see in the example, items will always contain all objects, and searchResults is just a filtered read-only view on that array.