Edit in JSFiddle

<div class="flex-container">
<div class="flex-item">flex item 1</div>
<div class="flex-item">flex item 2</div>
</div>
<button id="row" class="btn btn-default">row</button>
<button id="row-reverse" class="btn btn-default">row-reverse</button>
<button id="column" class="btn btn-default">column</button>
<button id="column-reverse" class="btn btn-default">column-reverse</button>

var container = $(".flex-container");
$(document).on('click','button',function(){
    var id = $(this).attr('id');
    container.css('flex-direction',id);
});

.flex-container {
    display: -webkit-flex;
    display: flex;
    flex-direction: row;
    width: 300px;
    height: 240px;
    background-color: Silver;
}

.flex-item {
    background-color: DeepSkyBlue;
    width: 100px;
    height: 100px;
    margin: 5px;
}