count the number of images with alts on a twitter.com/USERNAME/media page

count-alts.js

function count(){
  const images = [...$('.stream-item img')].filter(x => {
    let classList = [...x.classList]
    return !(classList.includes('avatar') || classList.includes('avatar--circular') || classList.includes('Emoji'))
  })

  const alts = images.map(x => x.alt).filter(x => !!x)
  return Math.ceil(alts.length/images.length*100) + '% coverage'
}