jQuery_ajax报错：Uncaught TypeError

$.ajax({
  type: 'POST',
  url: url,
  data: formData,
  success: function(res){

  }
});

使用FormData上传图片时报错，如下：

Uncaught TypeError: Illegal invocation
    at i (jquery.min.js:2)
    at jt (jquery.min.js:2)
    at Function.w.param (jquery.min.js:2)
    at Function.ajax (jquery.min.js:2)
    at HTMLInputElement.<anonymous> (category.html:119)
    at HTMLDocument.dispatch (jquery.min.js:2)
    at HTMLDocument.y.handle (jquery.min.js:2)

解决办法：设置processData与contentType参数为false

$.ajax({
  type: 'POST',
  url: url,
  data: formData,
  processData: false,   // jQuery不要去处理发送的数据
  contentType: false,   // jQuery不要去设置Content-Type请求头
  success: function(res){

  }
});