valid_video_file.js

  validFile(file, success, error) {
    const MAX_VIDEO_SIZE = 1024 * 1024 * 100;
    const MAX_VIDEO_DURATION = 30;
    const SIZE_ERROR = 1;
    const DURATION_ERROR = 2;

    if (file.size() > MAX_VIDEO_SIZE) {
      error(SIZE_ERROR);
      return;
    }

    let video = document.createElement('video');
    video.preload = 'metadata';
    video.onloadedmetadata = function() {
      window.URL.revokeObjectURL(this.src);
      let duration = video.duration;
      if (duration > MAX_VIDEO_DURATION) {
        error(DURATION_ERROR);
        return;
      }
      success(file);
    };
    video.src = URL.createObjectURL(e.target.files[0]);
  }