// $direction：排列方式默认;row(横排)，column(竖排)
// $justify：横轴排列方式
// $align:纵轴排列方式
// $flex-wrap:换行方式，默认不换行，wrap:(换行)
@mixin flexBox($direction: row, $justify: null, $align: null, $flex-wrap: nul) {
    display: flex;
    display: -ms-flexbox;
    -ms-flex-direction: row;

    @if ($direction !=null) {
        flex-direction: $direction;
        -ms-flex-direction: $direction;
    }

    @if ($justify !=nul) {
        justify-content: $justify;
    }

    @if ($align !=nul) {
        align-items: $align;
    }

    @if ($flex-wrap !=nul) {
        flex-wrap: $flex-wrap;
        -ms-flex-wrap: $flex-wrap;
    }
}