indexArray

Maps each position of a list to a row.

Maps each position of a list to a row. Rows are created and removed only when the length changes; the row at position i stays, and its item() accessor follows the value at i.

Import#

import { indexArray } from "@shadow-js/core";

Signature#

function indexArray<T, U>(
  list: ListSource<T>,
  map: (item: () => T, index: number) => U,
  options?: { fallback?: () => U },
): Accessor<U[]>

Parameters#

Name	Description
`list`	Source list. `null`, `undefined` and `false` are an empty list.
`map`	Runs once per position, untracked, in the row's own root.
`options`	`fallback` is shown while the list is empty. Undefined: an empty list maps to `[]`.

Returns#

Accessor of the mapped rows, in the order of the input.

Throws#

Nothing itself. Reading the accessor rethrows what map or a row cleanup threw; several errors at once arrive as one AggregateError.

Examples#

import { createRoot, indexArray, useSignal } from "@shadow-js/core";

createRoot(() => {
  const [values] = useSignal(["a", "b"]);
  const cells = indexArray(values, (value, index) => `${index}: ${value()}`);
  console.log(cells()); // ["0: a", "1: b"]
});