如何将facebook iframe like按钮居中

<div id="fb-like-button"></div>

window.fbAsyncInit = function() {
  FB.init({
    appId      : 'your-app-id',
    xfbml      : true,
    version    : 'v13.0'
  });
  FB.Event.subscribe('xfbml.render', function() {
    centerFbLikeButton();
  });
};

function centerFbLikeButton() {
  var container = document.getElementById('fb-like-button');
  var iframe = container.getElementsByTagName('iframe')[0];
  if (iframe) {
    var containerWidth = container.offsetWidth;
    var iframeWidth = iframe.offsetWidth;
    var marginLeft = (containerWidth - iframeWidth) / 2;
    iframe.style.marginLeft = marginLeft + 'px';
  }
};

(function(d, s, id){
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) {return;}
  js = d.createElement(s); js.id = id;
  js.src = "https://connect.facebook.net/en_US/sdk.js#xfbml=1&version=v13.0&appId=your-app-id&autoLogAppEvents=1";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));

#fb-like-button {
  display: flex;
  justify-content: center;
}