axios配置后，post提交formdata

var fd = new FormData()
fd.append("file", files[0])
let config = {
    headers: {
        "Content-Type": "multipart/form-data"
    }
}
axios.post(that.uploadUrl, fd,config).then( res => {
    console.log(res)
}).catch( res => {
    console.log(res)
})