esmBot has a flexible command handler, allowing you to create new commands and categories simply by creating new files. This page will provide a reference for creating new commands.
## Directory Structure
The bot loads commands from subdirectories inside of the `commands` directory, which looks something like this by default:
```
commands
- fun
> cat.js
> ...
- general
> help.js
> ping.js
> ...
- image-editing
> caption.js
> speed.js
> ...
```
As you can see, each command is grouped into categories, which are represented by subdirectories. To create a new category, you can simply create a new directory inside of the `commands` directory, and to create a new command, you can create a new JS file under one of those subdirectories.
## Commnand Structure
It's recommended to use the `Command` class located in `classes/command.js` to create a new command in most cases. This class provides various parameters and fields that will likely be useful when creating a command. Here is a simple example of a working command file:
```js
import Command from "../../classes/command.js";
class HelloCommand extends Command {
async run() {
return "Hello world!";
}
static description = "A simple command example";
static aliases = ["helloworld"];
}
export default HelloCommand;
```
As you can see, the first thing we do is import the Command class. We then create a new class for the command that extends that class to provide the needed parameters. We then define the command function, which is named `run`. Some static parameters, including the command description and an alias for the command, `helloworld`, are also defined. Finally, once everything in the command class is defined, we export the new class to be loaded as a module by the command handler.
The default command name is the same as the filename that you save it as, excluding the `.js` file extension. If you ever want to change the name of the command, just rename the file.
The parameters available to your command consist of the following:
-`this.client`: An instance of an Eris [`Client`](https://abal.moe/Eris/docs/Client), useful for getting info or performing lower-level communication with the Discord API.
-`this.ipc`: An eris-fleet [`IPC`](https://danclay.github.io/eris-fleet/classes/IPC.html) instance, useful for communication between worker processes.
-`this.origOptions`: The raw options object provided to the command by the command handler.
-`this.type`: The type of message that activated the command. Can be "classic" (a regular message) or "application" (slash commands).
-`this.channel`: An Eris [`TextChannel`](https://abal.moe/Eris/docs/TextChannel) object of the channel that the command was run in, useful for getting info about a server and how to respond to a message.
-`this.author`: An Eris [`User`](https://abal.moe/Eris/docs/User) object of the user who ran the command, or a [`Member`](https://abal.moe/Eris/docs/Member) object identical to `this.member` if run in a server as a slash command.
-`this.member`: An Eris [`Member`](https://abal.moe/Eris/docs/Member) object of the server member who ran the command. When running the command outside of a server, this parameter is undefined when run as a "classic" command or a [`User`](https://abal.moe/Eris/docs/User) object identical to `this.author` when run as a slash command.
-`this.options`: When run as a "classic" command, this is an object of special arguments (e.g. `--argument=true`) passed to the command. These arguments are stored in a key/value format, so following the previous example, `this.options.argument` would return true. When run as a slash command, this is an object of every argument passed to the command.
Some options are only available depending on the context/original message type, which can be checked with `this.type`. The options only available with "classic" messages are listed below:
-`this.message`: An Eris [`Message`](https://abal.moe/Eris/docs/Message) object of the message that the command was run from, useful for interaction.
-`this.args`: An array of text arguments passed to the command.
-`this.content`: A string of the raw content of the command message, excluding the prefix and command name.
-`this.reference`: An object that's useful if you ever decide to reply to a user inside the command. You can use [`Object.assign`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign) to combine your message content with this parameter.
-`flags`: An array of objects specifying command flags, or special arguments, that will be shown when running `help <command>` or a slash command. Example:
type: Constants.ApplicationCommandOptionTypes.STRING, // translates to 3, see https://discord.com/developers/docs/interactions/application-commands#application-command-object-application-command-option-type
The main JS code of your command is specified in the `run` function. This function should return a [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) of your command output, which is why the `run` function [is an async function by default](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function). The return value inside the `Promise` should be either a string or an object; you should return a string whenever you intend to reply with plain text, or an object if you intend to reply with something else, such as an embed or attachment.
