Axios interceptors don't send data to API in production Heroku app - vue.js

Question

This is part 2 of me debugging my application in production
In part 1, I managed to at least see what was causing my problem and managed to solve that.
When I send a request to my API which is hosted on Heroku using axios interceptor, every single request object looks like this in the API
{ 'object Object': '' }
Before sending out data to the API, I console.log() the transformRequest in axios and I can see that the data I am sending is actually there.
Note: I have tested this process simply using
axios.<HTTP_METHOD>('my/path', myData)
// ACTUAL EXAMPLE
await axios.post(
`${process.env.VUE_APP_BASE_URL}/auth/login`,
userToLogin
);
and everything works and I get data back from the server.
While that is great and all, I would like to abstract my request implementation into a separate class like I did below.
Does anyone know why the interceptor is causing this issue? Am I misusing it?
request.ts
import axios from "axios";
import { Message } from "element-ui";
import logger from "#/plugins/logger";
import { UsersModule } from "#/store/modules/users";
const DEBUG = process.env.NODE_ENV === "development";
const service = axios.create({
baseURL: process.env.VUE_APP_BASE_URL,
timeout: 5000,
transformRequest: [function (data) {
console.log('data', data)
return data;
}],
});
service.interceptors.request.use(
config => {
if (DEBUG) {
logger.request({
method: config.method,
url: config.url
});
}
return config;
},
error => {
return Promise.reject(error);
}
);
service.interceptors.response.use(
response => {
console.log('axios interception response', response)
return response.data;
},
error => {
const { response } = error;
console.error('axios interception error', error)
if (DEBUG) {
logger.error(response.data.message, response);
}
Message({
message: `Error: ${response.data.message}`,
type: "error",
duration: 5 * 1000
});
return Promise.reject({ ...error });
}
);
export default service;
Login.vue
/**
* Sign user in
*/
async onClickLogin() {
const userToLogin = {
username: this.loginForm.username,
password: this.loginForm.password
};
try {
const res = await UsersModule.LOGIN_USER(userToLogin);
console.log("res", res);
this.onClickLoginSuccess();
} catch (error) {
throw new Error(error);
}
}
UsersModule (VUEX Store)
#Action({ rawError: true })
async [LOGIN_USER](params: UserSubmitLogin) {
const response: any = await login(params);
console.log('response in VUEX', response)
if (typeof response !== "undefined") {
const { accessToken, username, name, uid } = response;
setToken(accessToken);
this.SET_UID(uid);
this.SET_TOKEN(accessToken);
this.SET_USERNAME(username);
this.SET_NAME(name);
}
}
users api class
export const login = async (data: UserSubmitLogin) => {
return await request({
url: "/auth/login",
method: "post",
data
});
};

Answer 1

I'm not sure what you're trying to do with transformRequest but that probably isn't what you want.
A quote from the documentation, https://github.com/axios/axios#request-config:
The last function in the array must return a string or an instance of Buffer, ArrayBuffer, FormData or Stream
If you just return a normal JavaScript object instead it will be mangled in the way you've observed.
transformRequest is responsible for taking the data value and converting it into something that can actually be sent over the wire. The default implementation does quite a lot of work manipulating the data and setting relevant headers, in particular Content-Type. See:
https://github.com/axios/axios/blob/885ada6d9b87801a57fe1d19f57304c315703079/lib/defaults.js#L31
If you specify your own transformRequest then you are replacing that default, so none of that stuff will happen automatically.
Without knowing what you're trying to do it's difficult to advise further but you should probably use a request interceptor rather than transformRequest for whatever it is you're trying to do.