Getting the baseline of a certain font

Stack Overflow: <a href="http://stackoverflow.com/questions/10247132/how-can-i-get-the-height-of-the-baseline-of-a-certain-font">How can I get the height of the baseline of a certain font?</a>

User abernier created a clever jQuery plugin that calculates the baseline for a font rendered in a web page. It inserts two inline elements (one small, one tall, neither with descenders): "." and "A". baseline = top / height

var $, detectBaseline, _ref;

$ = (_ref = this.jQuery) != null ? _ref : require('jQuery');

detectBaseline = function(el) {
  var $bigA, $container, $smallA;
  if (el == null) {
    el = 'body';
  }
  $container = $('<div style="visibility:hidden;"/>');
  $smallA = $('<span style="font-size:0;">A</span>');
  $bigA = $('<span style="font-size:999px;">A</span>');
  $container.append($smallA).append($bigA).appendTo(el);
  setTimeout((function() {
    return $container.remove();
  }), 10);
  return $smallA.position().top / $bigA.height();
};

$.fn.baseline = function() {
  return detectBaseline(this.get(0));
};