How to add/insert an item into an ObservableArray at a certain position with Knockout.js

javascript mvvm knockout.js
Mark Robinson picture Mark Robinson · Sep 6, 2011 · Viewed 44.2k times · Source

All the knockout examples I have found seem to add a new item to the end of an ObservableArray using something like:

viewModel.SomeItems.push(someNewItem);

This of course places the item at the end of the array.

How to I add an item to the ObservableArray at a certain position?

eg. something like:

viewModel.SomeItems.push(someNewItem, indexToInsertItAt);

Answer

ipr101 picture ipr101 · Sep 6, 2011

You should be able to use the native JavaScript splice method -

viewModel.SomeItems.splice(2,0,someNewItem);

Docs here - https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/splice

Example here (not Knockout specific) - How to insert an item into an array at a specific index?

From the Knockout docs -

For functions that modify the contents of the array, such as push and splice, KO’s methods automatically trigger the dependency tracking mechanism so that all registered listeners are notified of the change, and your UI is automatically updated.

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