octokit-rest/examples/getReleaseAsset.js

const octokit = require('@octokit/rest')({
  debug: true
})

octokit.repos.getReleases({
  owner: 'octokit',
  repo: 'rest.js'
})

  .then(result => {
    if (result.data.length === 0) {
      console.log('Repository has no releases')
      return
    }

    // get id of first release
    const firstRelease = result.data.pop()
    return octokit.repos.getAssets({
      owner: 'octokit',
      repo: 'rest.js',
      id: firstRelease.id
    })
  })

  .then(result => {
    if (result.data.length === 0) {
      console.log('First release has no assets attached')
      return
    }

    // get id of first asset
    const assetId = result.data[0].id
    return octokit.repos.getAsset({
      owner: 'octokit',
      repo: 'rest.js',
      id: assetId
    })
  })

  .then(result => {
  // result.data has asset properties
  })