formdata 图片上传

<input type="file" name="image" onchange="update">
<script>
    update(e) {
        let file = e.target.files[0]
        let params = new FormData()
        let filename = file.name
        if (!isImagesFlie(filename)) {
            alert('请选择符合格式要求的图片')
            e.target.value = ''
            return false
        }
        let fileSizeK = file.size
        if (fileSizeK >= 5242880) {
            alert('上传图片不能大于5M')
            e.target.value = ''
            return false
        }
        params.append('file', file)
        let config = {
            headers: {
                'Content-Type': 'multipart/form-data'
            }
        }
        axios.post(http://**, params, config).then((res) => {
            console.log(res)
        })
    }
</script>