gitlab-org--gitlab-foss/doc/development/fe_guide/axios.md

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# Axios
We use [Axios](https://github.com/axios/axios) to communicate with the server in Vue applications and most new code.
In order to guarantee all defaults are set you *should not use Axios directly*, you should import Axios from `axios_utils`.
## CSRF token
All our requests require a CSRF token.
To guarantee this token is set, we are importing [Axios](https://github.com/axios/axios), setting the token, and exporting `axios` .
This exported module should be used instead of directly using Axios to ensure the token is set.
## Usage
```javascript
import axios from './lib/utils/axios_utils';
axios.get(url)
.then((response) => {
// `data` is the response that was provided by the server
const data = response.data;
// `headers` the headers that the server responded with
// All header names are lower cased
const paginationData = response.headers;
})
.catch(() => {
//handle the error
});
```
## Mock Axios response in tests
To help us mock the responses we are using [axios-mock-adapter](https://github.com/ctimmerm/axios-mock-adapter).
Advantages over [`spyOn()`](https://jasmine.github.io/api/edge/global.html#spyOn):
- no need to create response objects
- does not allow call through (which we want to avoid)
- clear API to test error cases
- provides `replyOnce()` to allow for different responses
We have also decided against using [Axios interceptors](https://github.com/axios/axios#interceptors) because they are not suitable for mocking.
### Example
```javascript
import axios from '~/lib/utils/axios_utils';
import MockAdapter from 'axios-mock-adapter';
let mock;
beforeEach(() => {
// This sets the mock adapter on the default instance
mock = new MockAdapter(axios);
// Mock any GET request to /users
// arguments for reply are (status, data, headers)
mock.onGet('/users').reply(200, {
users: [
{ id: 1, name: 'John Smith' }
]
});
});
afterEach(() => {
mock.restore();
});
```
### Mock poll requests in tests with Axios
Because a polling function requires a header object, we need to always include an object as the third argument:
```javascript
mock.onGet('/users').reply(200, { foo: 'bar' }, {});
```