Recursive function using ES8 async/await ( see https://medium.com/@softwarecf/a-faint-outline-2a2c641d6492 )

getChildren.js

async function getChildren (id = 0) {
  let childRows = await runJxa(readChildren, [id])
  let result = await Promise.all(childRows.map(async child => {
    let {hasChildren, ...resultChild} = child
    if (!child.hasChildren) return resultChild
    return {...resultChild, children: await getChildren(child.id)}
  }))
  return result