Bootstrap的popover(弹出框)在append后弹不出(失效)

<button type="button" class="btn btn-default" data-container="body" data-toggle="popover" data-placement="" data-content="Vivamus sagittis lacus vel augue laoreet rutrum faucibus.">
 Popover on 顶部
</button>

<script>
$(function () {
 $('[data-toggle="popover"]').popover()
})
</script>

 var testHtml = "<button type='button' class='btn btn-default' data-container='body' data-toggle='popover' data-placement='' data-content='Vivamus sagittis lacus vel augue laoreet rutrum faucibus.'>"+
     "Popover on 顶部"+
    "</button>"

 $("body").append(testHtml);
 $('[data-toggle="popover"]').popover(); //创建popover（弹出框）DOM后立即初始化