Preload entire video using fetch, returns promise

preloadVideo.js

// Preloads entire video, returns promise
// NOTE: if a video doesn't exist the fetch will resolve, 
// but with a Blob type of `plain/text`
function preloadVideo(src) {
  return new Promise((resolve, reject) => {
    fetch(src)
      .then(response => response.blob())
      .then(blob => 
        /^video\/\w*/.test(blob.type)
          ? resolve(URL.createObjectURL(blob))
          : reject()
      )
      .catch(reject)
  })
}