未定义formData

Question

我有一个上传文件的回调。相当标准：

function sendFile(file) {
    formData = new FormData()
    formData.append('photo[uploaded_image]', file)
    $.ajax({
      data: formData,
      type: 'POST',
      url: '/photos',
      contentType: false,
      processData: false,
      success: function(response) {
          console.log(`uploaded ${response.photo}`)
      },
      error: function(response) {
          console.log(`couldn't upload: ${response}.`)
      }
})

为什么会出现此错误

未捕获的ReferenceError：未定义formData

在功能的第2行上？

formData = new FormData()