axios请求接口如何将data转换formdata？

methods: {

    data_to_string(data) {
                let tmp = new FormData();
                for (var key in data) {
                    tmp.append(key, data[key])
                }
                return tmp
            },

}


axios({data: this.data_to_string(this.form),})    #将data数据转换为formdata