CodePen

HTML

            
              <div class="container">
  <div class="gradient"></div>
</div>
            
          
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CSS

            
              body {
  background: #222;
  margin:0px;
  padding:50px 0;
}

.container {
  overflow: hidden;
}

.gradient {
  width: 300%;
  height: 10px;
  
  background: linear-gradient(to right,  rgba(109,179,242,1) 40%,rgba(255,255,255,1) 50%,rgba(109,179,242,1) 60%);
  position: relative;
  
  animation: move 3s infinite;
  animation-timing-function: linear; 
}

@keyframes move {
  0% {
    left: 0%;
  }
  
  100% {
    left: -200%;
  }
}
            
          
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JS

            
              
            
          
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