scss中 transition的动态写法

$duration:0.2s;
@mixin transition($props) {
    $transition: (); //声明空变量
    @for $i from 1 through length($props) { //循环$props
        $transition: append( //每次附加
            $transition,
            (nth($prop, $i) $duration), //nth是取变量
            $separator: comma //设置分隔符为逗号，不写默认为空格
        );
    }
    transition: $transition;
}

//scss input:
@include transition(height width transform);

//css output:
transition: height 0.2s, width 0.2s, transform 0.2s;