jQuery点击头像上传并预览图片

DS.upfile = function(){
  $('.img_show').each(function(){
   var $this = $(this),
    btn = $this.find('.upfile'),
    img = $this.find('img');
   btn.on('change',function(){
    var file = $(this)[0].files[0],
     imgSrc = $(this)[0].value,
     url = URL.createObjectURL(file);
    if (!/\.(jpg|jpeg|png|JPG|PNG|JPEG)$/.test(imgSrc)){
     alert("请上传jpg或png格式的图片！");
     return false;
    }else{
     img.attr('src',url);
     img.css({'opacity':'1'});
    }
   });
  });
 }();