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     | value                                                                             |
| ------------------------- | -------- | :-------------------------------------------------------------------------------- |
| blockerComponent          | node     | can be either `null` or React node (e.g. `() => <div />`)                         |
| blockerComponentProps     | object   | `{}`                                                                              |
| description               | string   | `My awesome plugin`                                                               |
| 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)             |
| leftMenuLinks             | array    | `[]`                                                                              |
| lifecycles                | function | Refer to the [Lifecycle documentation](#lifecycle)                                |
| mainComponent             | node     | The plugin's App container                                                        |
| preventComponentRendering | boolean  | Wheter or not display the plugin's blockerComponent instead of the main component |
| 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.

:::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>;
  }
}
```