Sass mixin可快速添加渐变

@mixin background-gradient($start-color, $end-color, $orientation) { 
    background: $start-color;

    @if $orientation == 'vertical' {
      background: -webkit-linear-gradient(top, $start-color, $end-color);
      background: linear-gradient(to bottom, $start-color, $end-color);
    } @else if $orientation == 'horizontal' {
      background: -webkit-linear-gradient(left, $start-color, $end-color);
      background: linear-gradient(to right, $start-color, $end-color);
    } @else {
      background: -webkit-radial-gradient(center, ellipse cover, $start-color, $end-color);
      background: radial-gradient(ellipse at center, $start-color, $end-color);
    }
}
 //Usage:
 //$start-color, $end-color, $orientation - vertical/horizontal/radial
 .foo {
    @include background-gradient(red, black, 'vertical');
  }
  //Output
  .foo {
    background: -webkit-linear-gradient(top, red, black);
    background: linear-gradient(to bottom, red, black);
  }