CSS animate star rating one by one

I have the following HTML:

<div class="rating">
  <div class="star active"></div>
  <div class="star active"></div>
  <div class="star active"></div>
  <div class="star"></div>
  <div class="star"></div>
</div>

Output:

★★★☆☆

How do I animate in CSS the active stars, one by one?

I tried:

.star {
   transition: background-color 0.5s ease;
   background-color: #eee;
}

.star.active { 
   background-color: #000;
}

This transitions the color of all the active stars at once. How to I transition the active stars one by one, from left to right?

I am trying to achieve this without JS. The rating score can be anything. Also the range can be any number (there could be 3 or 5 or 8 or 10 stars, etc)

Answers:

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Method 1

Because of the active class is already assigned, it’s better to use animation instead of transition.

.star {
  background-color: #eee;
}

.star.active {
  animation: star-pop 0.5s ease forwards;
}

@keyframes star-pop {
   to {
      background-color: #000;
   }
}

Then you can give a different animation-delay for different nth-child:

.star.active:nth-child(1) { 
   animation-delay: 0s;
}

.star.active:nth-child(2) { 
   animation-delay: 0.5s;
}

.star.active:nth-child(3) { 
   animation-delay: 1s;
}

.star.active:nth-child(4) { 
   animation-delay: 1.5s;
}

.star.active:nth-child(5) { 
   animation-delay: 2s;
}

/* ... */

If you have a css precompiler(such as sass), you can achieve it with a loop:

.star.active {
   // change the number 5 to maximum possible stars(8, 10, etc.)
   @for $i from 1 through 5 {
      &:nth-child(#{$i}) {
         animation-delay: #{($i - 1) * 0.5}s;
      }
   }
}

.star {
  display: inline-block;
  width: 40px;
  height: 40px;
  border: solid 1px #000;
  background-color: #eee;
}

.star.active {
  animation: star-pop 0.5s ease forwards;
}


.star.active:nth-child(1) { 
   animation-delay: 0s;
}

.star.active:nth-child(2) { 
   animation-delay: 0.5s;
}

.star.active:nth-child(3) { 
   animation-delay: 1s;
}

.star.active:nth-child(4) { 
   animation-delay: 1.5s;
}

.star.active:nth-child(5) { 
   animation-delay: 2s;
}

@keyframes star-pop {
   to {
      background-color: #000;
   }
}

<div class="rating">
  <div class="star active"></div>
  <div class="star active"></div>
  <div class="star active"></div>
  <div class="star"></div>
  <div class="star"></div>
</div>

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0