article.ts

function findAnnotations (field:Block | Inline):Array<Block | Inline> {
  const annotations:Array<Block | Inline> = []

  // `field.content` returns Block | Inline | Text
  // I’d like to ignore Text
  // `reduce` is showing a TypeScript error "This expression is not callable" because Text isn’t included
  // but if I add it, `node.content` errors because Text doesn’t have `.content`
  return field.content.reduce((acc:Array<Block | Inline>, node:Block | Inline) => {
    if (node.nodeType === INLINES.EMBEDDED_ENTRY && node.data.target.sys.contentType.sys.id === 'annotation') {
      acc.push(node.data.target)
    } else if (node.content && node.content.length > 0) {
      acc.push(...this.findAnnotations(node))
    }

    return acc
  }, annotations)
}