Gif creator jscript part 1

giftCreator1.js

//Set up Image and video uploaders:
      window.addEventListener('load', async function() {

        //Image loader:
        imageUploadButton.addEventListener('change', async function() {

          if (videoDownloadLink) videoDownloadLink.remove();

          if (this.files && this.files[0]) {

            imgTag.onload = () => {
              URL.revokeObjectURL(imgTag.src); // no longer needed, free memory
            }

            imgTag.src = URL.createObjectURL(this.files[0]); // set src to blob url

            //Generate blob from url:
            let blob = await fetch(imgTag.src).then(r => r.blob());

            //Convert image to buffer Array:
            retreiveImage(blob);

            // show convert button
            button.classList.remove('hidden', 'gray');

            uploadButtons.classList.add('hidden');

            //Set to convert gif to video:
            button.removeEventListener('click', convertVideo2Gif);
            button.removeEventListener('click', convertGifToMp4);

            //Attach run command to convert button
            button.addEventListener('click', convertGifToMp4);

          }
        });

        inputTag.addEventListener('change', readVideo);

        //Read video from url
        async function readVideo(event) {

          if (videoDownloadLink) videoDownloadLink.remove();

          if (event.target.files && event.target.files[0]) {

            fileName = event.target.files[0];

            var srcResult = URL.createObjectURL(event.target.files[0]);

            videoTag.onload = () => {
              URL.revokeObjectURL(srcResult); // no longer needed, free memory
            }

            videoTag.src = srcResult;

            videoTag.play();

            videoTag.classList.remove('hidden');

            //Generate blob from url:
            let blob = await fetch(srcResult).then(r => r.blob());

            //Convert image to buffer Array:
            retreiveVideo(event.target.files[0]);

          }


          uploadButtons.classList.add('hidden');


          // show convert button
          button.classList.remove('hidden', 'gray');

          //Attach run command to convert button
          button.removeEventListener('click', convertVideo2Gif);
          button.removeEventListener('click', convertGifToMp4);

          button.addEventListener('click', convertVideo2Gif);

        }

      });



      //Push to arrayBuffer of image
      function retreiveImage(blob) {

        var fileReader = new FileReader();

        fileReader.onload = function(event) {
          sampleImageData = new Uint8Array(event.target.result);
        };

        fileReader.readAsArrayBuffer(blob);

      }


      //Push to arrayBuffer of video
      function retreiveVideo(file) {

        var fileReader = new FileReader();

        fileReader.onload = function(event) {

          sampleVideoData = new Uint8Array(event.target.result);

        };

        fileReader.readAsArrayBuffer(file);

      }