@ocelot-consulting/hummus-toc/src/writeOutline.js

An extension for HummusJS to add Table of Contents (including bookmarks).

const writeOutlines = (ctx, outlines, parent, linkToTop = true) => {
  const ids = outlines.map(() => ctx.allocateNewObjectID())

  outlines.forEach(({ title, page, children }, i) => {
    const id = ids[i]
    const childrenIds = children && children.length ? writeOutlines(ctx, children, id) : null

    ctx.startNewIndirectObject(id)
    const d = ctx.startDictionary()
      .writeKey('Title')
      .writeLiteralStringValue(title)
      .writeKey('Parent')
      .writeObjectReferenceValue(parent)

    if (page) {
      d.writeKey('Dest')
      ctx.startArray()
      ctx.writeIndirectObjectReference(page)
      ctx.writeName('XYZ')
      const c = ctx.startFreeContext()
      if (linkToTop) {
        c.write([ 32, 48, 32, 55, 57, 50, 32, 48, 32 ]) // " 0 792 0 " - go to top
      } else {
        c.write([ 32, 110, 117, 108, 108, 32, 110, 117, 108, 108, 32, 48, 32 ]) // " null null 0 " - stay at same position
      }
      ctx.endFreeContext()
      ctx.endArray()
    }

    ctx.endLine()
    if (childrenIds) {
      d.writeKey('Count')
        .writeNumberValue(outlines.length)
        .writeKey('First')
        .writeObjectReferenceValue(childrenIds[0])
        .writeKey('Last')
        .writeObjectReferenceValue(childrenIds[childrenIds.length - 1])
    }

    if (i + 1 < ids.length) {
      d.writeKey('Next')
        .writeObjectReferenceValue(ids[i + 1])
    }

    if (i > 0) {
      d.writeKey('Prev')
        .writeObjectReferenceValue(ids[i - 1])
    }

    ctx.endDictionary(d)
    ctx.endIndirectObject()
  })
  return ids
}

module.exports = (ctx, outlines) => {
  if (outlines.length === 0) {
    return null
  }

  const outline = ctx.allocateNewObjectID()
  const outlineIds = writeOutlines(ctx, outlines, outline)
  ctx.startNewIndirectObject(outline)
  const d = ctx.startDictionary()
    .writeKey('Type')
    .writeNameValue('Outlines')
    .writeKey('Count')
    .writeNumberValue(outlineIds.length)
    .writeKey('First')
    .writeObjectReferenceValue(outlineIds[0])
    .writeKey('Last')
    .writeObjectReferenceValue(outlineIds[outlineIds.length - 1])
  ctx.endDictionary(d)
  ctx.endIndirectObject()
  return outline
}