Get an image preview from a video URL with vainilla JavaScript

fetchVideoThumb.js

// make a data uri encoded image from a <video> element using canvas
// (thank you stackoverflow people)
function videoElementToImage(videoElement, width, height) {
    width = width || 360;
    height = height || 240;
    var canvas = document.createElement('canvas');
    canvas.width = width; 
    canvas.height = height;
    var context = canvas.getContext('2d');
    context.drawImage(videoElement, 0, 0, canvas.width, canvas.height);
    var dataURI = canvas.toDataURL('image/jpeg');
    // discard created canvas element
    canvas = null;
    return dataURI;
}
// get a data uri encoded image from a video URL
function fetchVideoThumb(url, width, height) {
    width = width || 360;
    height = height || 240;
    // will be async as we need to wait some frame to be downloaded
    return new Promise(function(resolve, reject) {
        var video = document.createElement('video');
        video.width = width;
        video.height = height;
        video.attributes['preload'] = 'none';
        // first setup the listeners
        video.addEventListener('loadeddata', function() {
            var dataURI = videoElementToImage(video, width, height);
            // cleanup so loading ends
            video = null;
            // we're done, here's your thumb:
            resolve(dataURI);
        });
        video.addEventListener('error', function() {
            // remove element in case of error
            video = null;
            reject();
        });
        // then set url so load begin
        video.src = url;
    });
}

main.js

var someImage = new Image();
var someElement = document.createElement('div');

// usage:
fetchVideoThumb('/videos/1234.mp4').then(function(thumb) {
  someImage.src = thumb;
  // or
  someElement.style['background-image'] = thumb;
}, function() {
  console.log('couldnt load the video!');
});

MIT LICENSE
Copyright <2018>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.