Factory options

makeTreeFactory<V>(options) accepts:

Option	Default	Description
cornerCellValue	— (required)	Value of the top-left corner cell above lifted header bands.
createHeader	— (required)	(key, record) => leaf — header cell for an object key.
createIndex	— (required)	(i, array) => leaf — index cell for array item i.
createLeaf	identity	(value) => leaf — formats data leaves (joined arrays included). Headers, indexes, corners and filler never pass here.
joinArrayValues	undefined	(values) => leaf | undefined — merges an array into one leaf; return undefined to render it as a table. Receives raw input order, before key stabilization. Use joinPrimitiveArrayValues to comma-join all-primitive arrays.
emptyCellValue	() => ""	({ type, width, height }) => leaf — placeholder for content-less cells. type is "gap" (sizing filler), "empty-array" or "empty-object".
isProportionalResize	allows 100% growth	(lcm, max) => boolean — guards LCM-scaling of sibling heights. Use makeProportionalResizeGuard(threshold); when it rejects, short columns are padded with filler instead.
collapseIndexes	false	Flatten nested arrays into dotted index paths (1.2, …) instead of nested index columns.
stabilizeOrderOfPropertiesInArraysOfObjects	true	Reorder keys of objects inside an array by stable first-seen position, so columns line up.
deduplicateHeaders	true	Lift the header band common to all array items on top of the table. Set false to keep per-row headers.
isHeaderEqual	Object.is	(a, b) => boolean — custom equality for header values during band lifting. Needed when headers carry objects (see below).

Input handling

• Objects with a toJSON() method are unwrapped via toJSON() first.
• Objects exposing a [TO_TABLE]() method (import TO_TABLE from @json-table/core) bypass parsing with their prebuilt Tree.
• Every array level renders its index column — no special cases, so [x] stays distinguishable from x and [{ ... }] from { ... }. joinArrayValues runs before that, uniformly (empty arrays never reach it: they render as the emptyCellValue filler). In collapseIndexes mode nested levels flatten into dotted paths ([[123]] → 1.1 | 123); a flat singleton ([x]) flattened nothing and renders bare, as do empty arrays.
• Empty arrays render as one empty-array filler cell, empty objects as one empty-object filler cell (see emptyCellValue).
• Headers carrying objects never lift by identity alone: pass isHeaderEqual to compare them (e.g. by label).