For and Index

For

For renders one row per item. With keyBy or key, rows are reused and moved when the array changes. The item is a plain value and index is an accessor.

A field that changes on an item with the same key does not render again. Keep such fields in a signal on the item, like done above, or use a store.

Index

Index is the other way round: the item is an accessor and the index a number. Rows stay in place and only their item changes. Use it for lists of primitives edited in place, and read item() inside a binding.