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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div class="video-container">
  <div class="lazy-loading-content image-container">
    <!--     Replace Youtube ID for Image thumbnail -->
    <img src="https://i.ytimg.com/vi/hJ7Rg1821Q0/maxresdefault.jpg" class="video-thumbnail" />
    <div class="play-button">
    </div>
  </div>
</div>
!

CSS 

              
                $spacer: 2rem;

.video-container {
  display: flex;
  align-items: center;
  justify-content: center;
  margin: $spacer;
  padding: $spacer;

  &:hover {
    cursor: pointer;
    .play-button {
      filter: none;
    }
  }

  .image-container {
    width: 100%;
    position: relative;

    img {
      vertical-align: middle;
      width: 100%;
      height: auto;
    }
  }
}

.play-button {
  width: 68px;
  height: 48px;
  position: absolute;
  transform: translate3d(-50%, -50%, 0);
  top: 50%;
  left: 50%;
  z-index: 1;
  background-color: transparent;
  /* youtube's actual play button svg */
  background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 68 48"><path fill="%23f00" fill-opacity="0.8" d="M66.52,7.74c-0.78-2.93-2.49-5.41-5.42-6.19C55.79,.13,34,0,34,0S12.21,.13,6.9,1.55 C3.97,2.33,2.27,4.81,1.48,7.74C0.06,13.05,0,24,0,24s0.06,10.95,1.48,16.26c0.78,2.93,2.49,5.41,5.42,6.19 C12.21,47.87,34,48,34,48s21.79-0.13,27.1-1.55c2.93-0.78,4.64-3.26,5.42-6.19C67.94,34.95,68,24,68,24S67.94,13.05,66.52,7.74z"></path><path d="M 45,24 27,14 27,34" fill="%23fff"></path></svg>');
  filter: grayscale(100%);
  transition: filter 0.1s cubic-bezier(0, 0, 0.2, 1);
  border: none;
}
!

JS 

              
                // update variable with the Youtube Video ID
const videoID = "dQw4w9WgXcQ";

// selects the parent container
const parentContainer = document.querySelector(".video-container");

// When the parent container is clicked
parentContainer.addEventListener("click", function () {
  // remove the image container
  const lazyLoadingChild = document.querySelector(".lazy-loading-content");
  parentContainer.removeChild(lazyLoadingChild);

  // create a new responsive video container
  const responsiveVideoContainer = document.createElement("div");

  // apply responsive classes from bootstrap
  responsiveVideoContainer.classList.add(
    "embed-responsive",
    "embed-responsive-16by9"
  );

  // create the iFrame with the video embed
  const videoIframe = document.createElement("iframe");

  videoIframe.classList.add("embed-responsive-item");

  videoIframe.src = `https://www.youtube.com/embed/${videoID}?autoplay=1&mute=1`;

  videoIframe.setAttribute("allow", "autoplay");

  // add the iFrame to the video container
  responsiveVideoContainer.appendChild(videoIframe);

  // add the video container to the parent container
  parentContainer.appendChild(responsiveVideoContainer);
});
!
999px

Console