<!DOCTYPE html>
<html>
<head lang="en">
  <meta charset="UTF-8">
  <title></title>
  <style>
    #box {
      width: 100%;
    }

    #content {
      display: inline-block;
      width: 100%;
    }
  </style>
</head>
<body>
<div id="box">
  <p id="content">
　　Lorem ipsum dolor sit amet, consectetur adipisicing elit. Atque blanditiis consequatur dicta et hic laborum, minus molestiae perspiciatis placeat quam quia quo recusandae reiciendis sapiente sequi tempore tenetur voluptatibus? Praesentium!
　　</p>
</div>
<script src="js/jquery-1.11.3.js"></script>
<script>
  $.fn.fontFlex = function(min, max, mid) {
    var $this = this;
    $(window).resize(function() {
      var size = window.innerWidth / mid;
      if (size < min) {
        size = min
      }
      if (size > max) {
        size = max
      }
      $this.css('font-size', size + 'px');
      console.log(window.innerWidth);
    }).trigger('resize');
  };
  $('#content').fontFlex(20,60,40)
</script>
</body>
</html>
jq的resize()事件 ，检测浏览器窗口的重置（改变）
trigger()触发某个事件
在最小font-size和最大font-size之间改变浏览器窗口大小实现fs自适应。