ANGULARJS: sorting direction up/down using css

.caret {
    border: 5px solid transparent;
    display: inline-block;
    width: 0;
    height: 0;
    opacity: 1;
    color:
    vertical-align: top;
}

.caret.up {
    border-bottom: 5px solid #fff;
}

.caret.right {
    border-left: 5px solid #fff;
}

.caret.down {
    border-top: 5px solid #fff;
}

.caret.left {
    border-right: 5px solid #fff;
}

<span class='caret' ng-class="{down:sortingTarget==m.Id&& sortingDirection,up:sortingTarget==m.Id&& !sortingDirection}"></span>