strapi/docs/3.0.0-beta.x/plugin-development/frontend-development.md

# Front-end Development

Strapi's admin panel and plugins system aim to be an easy and powerful way to create new features.

The admin panel is a [React](https://facebook.github.io/react/) application which can embed other React applications. These other React applications are the `admin` parts of each Strapi's plugins.

## Environment setup

To enable local plugin development, you need to start your application with the front-end development mode activated:

```bash
$ cd my-app
$ yarn develop --watch-admin
```

## API

### Strapi global variable

The administration exposes a global variable that is accessible for all the plugins.

#### `strapi.backendURL`

Retrieve the back-end URL. (e.g. `http://localhost:1337`).

#### `strapi.currentLanguage`

Retrieve the administration panel default language (e.g. `en-US`)

#### `strapi.languages`

Array of the administration panel's supported languages. (e.g. `['ar', 'en', 'fr', ...]`).

#### `strapi.lockApp()`

Display a loader that will prevent the user from interacting with the application.

#### `strapi.unlockApp()`

Remove the loader so the user can interact with the application

#### `strapi.notification`

Display a notification (works with i18n message id). Use this command anywhere in your code.

```js
strapi.notification.error('app.notification.error');
strapi.notification.info('app.notification.info');
strapi.notification.success('app.notification.success');
strapi.notification.warning('app.notification.warning');
```

#### `strapi.remoteURL`

The administration url (e.g. `http://localhost:4000/admin`).

### Main plugin object

Each plugin exports all its configurations in an object. This object is located in `my-plugin/admin/src/index.js`

Here are its properties:

| key                       | type    | Description                                                                                                                                                                                                             |
| ------------------------- | ------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| blockerComponent          | node    | Props can be either `null` or React node (e.g. `() => <div />`)                                                                                                                                                         |
| blockerComponentProps     | object  | Props to provide to customise the [blockerComponent](https://github.com/strapi/strapi/blob/58588e10e5d15921b0966e20ce1bc6cde70df5cc/packages/strapi-helper-plugin/lib/src/components/BlockerComponent/index.js#L81-L86) |
| description               | string  | Plugin's description retrieved from the package.json                                                                                                                                                                    |
| id                        | string  | Id of the plugin from the `package.json`                                                                                                                                                                                |
| initializer               | node    | Refer to the [Initializer documentation](#initializer)                                                                                                                                                                  |
| injectedComponents        | array   | Refer to the [Injected Component documentation](#injected-components)                                                                                                                                                   |
| isReady                   | boolean | The app will load until this proprety is true                                                                                                                                                                           |
| leftMenuLinks             | array   | Array of links to inject in the menu                                                                                                                                                                                    |
| mainComponent             | node    | The plugin's App container, setting it to null will prevent the plugin from being displayed in the menu                                                                                                                 |
| name                      | string  | The plugin's name retrieved from the package.json                                                                                                                                                                       |
| pluginLogo                | file    | The plugin's logo                                                                                                                                                                                                       |
| preventComponentRendering | boolean | Whether or not display the plugin's blockerComponent instead of the main component                                                                                                                                      |
| settings                  | object  | Refer to the [Plugins settings API](./frontend-settings-api.md)                                                                                                                                                         |
| reducers                  | object  | The plugin's redux reducers                                                                                                                                                                                             |
| trads                     | object  | The plugin's translation files                                                                                                                                                                                          |

### Initializer

The component is generated by default when you create a new plugin. Use this component to execute some logic when the app is loading. When the logic has been executed this component should emit the `isReady` event so the user can interact with the application.

::: tip NOTE
Below is the Initializer component of the content-type-builder plugin.

It checks whether or not the autoreload feature is enabled and depending on this value changes the mainComponent of the plugin.
:::

```js
/**
 *
 * Initializer
 *
 */

import React from 'react';
import PropTypes from 'prop-types';

import pluginId from '../../pluginId';

class Initializer extends React.PureComponent {
  // eslint-disable-line react/prefer-stateless-function
  componentDidMount() {
    const {
      admin: { autoReload, currentEnvironment },
    } = this.props;

    let preventComponentRendering;
    let blockerComponentProps;

    if (currentEnvironment === 'production') {
      preventComponentRendering = true;
      blockerComponentProps = {
        blockerComponentTitle: 'components.ProductionBlocker.header',
        blockerComponentDescription: 'components.ProductionBlocker.description',
        blockerComponentIcon: 'fa-ban',
        blockerComponentContent: 'renderButton',
      };
    } else {
      // Don't render the plugin if the server autoReload is disabled
      preventComponentRendering = !autoReload;
      blockerComponentProps = {
        blockerComponentTitle: 'components.AutoReloadBlocker.header',
        blockerComponentDescription: 'components.AutoReloadBlocker.description',
        blockerComponentIcon: 'fa-refresh',
        blockerComponentContent: 'renderIde',
      };
    }

    // Prevent the plugin from being rendered if currentEnvironment === PRODUCTION
    this.props.updatePlugin(pluginId, 'preventComponentRendering', preventComponentRendering);
    this.props.updatePlugin(pluginId, 'blockerComponentProps', blockerComponentProps);
    // Emit the event plugin ready
    this.props.updatePlugin(pluginId, 'isReady', true);
  }

  render() {
    return null;
  }
}

Initializer.propTypes = {
  admin: PropTypes.object.isRequired,
  updatePlugin: PropTypes.func.isRequired,
};

export default Initializer;
```

### Injected Components

(Coming soon)

### Routing

The routing is based on the [React Router V5](https://reacttraining.com/react-router/web/guides/philosophy), due to it's implementation each route is declared in the `containers/App/index.js` file.

::: tip
Each route defined in a plugin must be prefixed by the plugin's id.
:::

**Route declaration :**

Let's say that you want to create a route `/user` with params `/:id` associated with the container UserPage.

The declaration would be as follows :

**Path —** `plugins/my-plugin/admin/src/containers/App/index.js`.

```js
import React from 'react';
import pluginId from '../../pluginId';

import UserPage from '../UserPage';

// ...

class App extends React.Component {
  // ...

  render() {
    return (
      <div>
        <Switch>
          <Route exact path={`/plugins/${pluginId}/user/:id`} component={UserPage} />
        </Switch>
      </div>
    );
  }
}

// ...
```

### Styling

The administration panel uses [styled-components](https://styled-components.com/) for writing css.

### i18n

[React Intl](https://github.com/yahoo/react-intl) provides React components and an API to format dates, numbers, and strings, including pluralization and handling translations.

**Usage**

We recommend to set all your components text inside the translations folder.

The example below shows how to use i18n inside your plugin.

**Define all your ids with the associated message:**

**Path —** `./plugins/my-plugin/admin/src/translations/en.json`.

```json
{
  "notification.error.message": "An error occurred"
}
```

**Path —** `./plugins/my-plugin/admin/src/translations/fr.json`

```json
{
  "notification.error.message": "Une erreur est survenue"
}
```

**Usage inside a component**

**Path —** `./plugins/my-plugin/admin/src/components/Foo/index.js`.

```js
import { FormattedMessage } from 'react-intl';
import SomeOtherComponent from 'components/SomeOtherComponent';

const Foo = props => (
  <div className={styles.foo}>
    <FormattedMessage id="my-plugin.notification.error.message" />
    <SomeOtherComponent {...props} />
  </div>
);

export default Foo;
```

See [the documentation](https://github.com/yahoo/react-intl/wiki/Components#formattedmessage) for more extensive usage.

### Global context

All plugins are wrapped inside the `GlobalContextProvider`, in this object you will have access to all plugins object as well as other utilities.

Usage:

**Inside a functional component:**

```js
import React from 'react';
import { useGlobalContext } from 'strapi-helper-plugin';

const Foo = () => {
  const globalContext = useGlobalContext();

  console.log(globalContext);

  return <div>Foo</div>;
};
```

**Inside a class component:**

```js
import React from 'react';
import { GlobalContext } from 'strapi-helper-plugin';

class Foo extends React.Component {
  static contextType = GlobalContext;

  render() {
    console.log(this.context);

    return <div>Foo</div>;
  }
}
```