Javascript-骨架内容占位符

Question

此功能将显示:empty HTML元素的样式（设计为看起来像占位符），直到page load，然后将一些内容注入这些元素，从而删除:empty样式并显示内容。

如何在不使用:empty并通过JS注入现有HTML内容的情况下简单地显示占位符？我希望已经有h1，p和img的数据，并在page load期间为这些元素放一个占位符。

var
  image = document.querySelector('.sk-image'),
  heading = document.querySelector('.sk-heading'),
  paragraph = document.querySelector('.sk-paragraph');

var content = false;

document.addEventListener('DOMContentLoaded', function() {
  setTimeout(function() {
    if (content === false) {
      content = true;
      image.src = 'http://unsplash.it/400/400?image=564';
      heading.innerHTML = 'Some heading';
      paragraph.innerHTML = 'Lorem ipsum dolor sit amet, consectetur adipisicing elit. Culpa rerum porro aut laboriosam animi.';
    } else {
      content = false;
      image.src = '';
      heading.innerHTML = '';
      paragraph.innerHTML = '';
    }
  }, 2000);
}, false);

body {
  display: flex
}

.card {
  width: 100%;
  max-width: 300px;
  min-height: 400px;
  margin: 10px;
  background: #fff;
  border-bottom: 1px solid #d8d8d8;
  box-shadow: 0 1px 4px 0 rgba(0, 0, 0, 0.1);
}

.card__image {
  position: relative;
  width: 100%;
  height: 0;
  padding-bottom: 60%;
  background: #eee;
  overflow: hidden;
}

.card__image:after {
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, rgba(0, 0, 0, 0), rgba(255, 255, 255, 0.65), rgba(0, 0, 0, 0));
  transform: translateX(-100%);
  animation: loading 1.5s infinite;
}

.card__image img {
  position: relative;
  max-width: 100%;
  z-index: 1;
}

.card__content {
  padding: 20px;
}

.card__heading {
  margin-top: 0;
  margin-bottom: 10px;
  font-family: 'Alegreya Sans', sans-serif;
  font-weight: 400;
}

.card__heading:empty {
  width: 100%;
  height: 35px;
  background: #d8d8d8;
  margin-bottom: 20px;
}

.card__paragraph {
  margin: 0;
  font-size: 20px;
  line-height: 1.35;
}

.card__paragraph:empty {
  width: 90%;
  height: 20px;
  background: #d8d8d8;
}

.button {
  margin: 10px;
  padding: 15px 20px;
  background: #2aa1c0;
  border: 0;
  color: #fff;
}

.button:hover {
  background: #0e647d;
}

@-moz-keyframes loading {
  100% {
    transform: translateX(100%);
  }
}

@-webkit-keyframes loading {
  100% {
    transform: translateX(100%);
  }
}

@-o-keyframes loading {
  100% {
    transform: translateX(100%);
  }
}

@keyframes loading {
  100% {
    transform: translateX(100%);
  }
}

<div class="card">
  <div class="card__image">
    <img class="sk-image" alt="" />
  </div>
  <div class="card__content">
    <h1 class="card__heading sk-heading"></h1>
    <p class="card__paragraph sk-paragraph"></p>
  </div>
</div>
<div class="card">
  <div class="card__image">
    <img class="sk-image" alt="" />
  </div>
  <div class="card__content">
    <h1 class="card__heading sk-heading"></h1>
    <p class="card__paragraph sk-paragraph"></p>
  </div>
</div>