style.scss

@mixin gradient($color-stops...) {
    background: nth(nth($color-stops, 1), 1);
    background: -webkit-linear-gradient(to bottom, $color-stops);
    background: linear-gradient(to bottom, $color-stops);
}

@mixin keyframes($name) {
    @-webkit-keyframes #{$name} {
        @content;
    }
    @-moz-keyframes #{$name} {
        @content;
    }
    @-ms-keyframes #{$name} {
        @content;
    }
    @keyframes #{$name} {
        @content;
    }
}

$loader-color11: #1399d6;
$loader-color21: #de2890;
$loader-color22: #ff969f;
$loader-color31: #2d65c5;
$loader-color41: #8cd3ff;
$loader-color42: #1593ed;
$light-bg: #ffffff;

$loader-bars: 4;
$loader-bar-width: 10px;
$loader-margin: 2px;
$loader-height: 50px;
$loader-width: $loader-bars * ($loader-bar-width + 2 * $loader-margin);

@include keyframes(bar1){
  0% {
    height: $loader-height * 0.2;
  }
  25%{
    height: $loader-height * 0.5;
  }
  50% {
    height: $loader-height * 0.8;
  }
  75%{
    height: $loader-height;
  }
  100% {
    height: $loader-height * 0.2;
  }
}

.graph-loader-bg{
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: rgba($light-bg, 0.5);
  z-index: 9;
}

.graph-loader-wrapper{
  position: absolute;
  left: calc(50% - #{($loader-width / 2)});
  top: calc(50% - #{($loader-height / 2)});
  
  .loaders {
    display: block;
    height: $loader-height;
    margin: 0 $loader-margin;
    width: $loader-bar-width;
    position: relative;
    float: left;

    > div {
      animation-timing-function: ease-in-out;
      animation-duration: 1.1s;
      animation-name: bar1;
      animation-iteration-count: infinite;
      height: $loader-height * 0.4;
      position: absolute;
      bottom: 0;
      left: 0;
      right: 0;
    }
  }
  
  .loader1 {
    @include gradient($loader-color11);
  }
  .loader2 {
    animation-delay: 0.4s;
    @include gradient($loader-color21, $loader-color22);
  }
  .loader3 {
    animation-delay: 0.8s;
    @include gradient($loader-color31);
  }
  .loader4 {
    animation-delay: 0.6s;
    @include gradient($loader-color41, $loader-color42);
  }
}