command-concept.ts

// The Command Pattern Concept

interface ICommand {
    execute(): void
}

class Invoker {
    // The Invoker Class
    #commands: { [id: string]: ICommand }

    constructor() {
        this.#commands = {}
    }

    register(commandName: string, command: ICommand) {
        // Register commands in the Invoker
        this.#commands[commandName] = command
    }

    execute(commandName: string) {
        // Execute any registered commands
        if (commandName in this.#commands) {
            this.#commands[commandName].execute()
        } else {
            console.log(`Command [${commandName}] not recognised`)
        }
    }
}

class Receiver {
    // The Receiver

    runCommand1() {
        // A set of instructions to run
        console.log('Executing Command 1')
    }

    runCommand2() {
        // A set of instructions to run
        console.log('Executing Command 2')
    }
}

class Command1 implements ICommand {
    // A Command object, that implements the ICommand interface and
    // runs the command on the designated receiver

    #receiver: Receiver

    constructor(receiver: Receiver) {
        this.#receiver = receiver
    }

    execute() {
        this.#receiver.runCommand1()
    }
}

class Command2 implements ICommand {
    // A Command object, that implements the ICommand interface and
    // runs the command on the designated receiver

    #receiver: Receiver

    constructor(receiver: Receiver) {
        this.#receiver = receiver
    }

    execute() {
        this.#receiver.runCommand2()
    }
}

// The Client
// Create a receiver
const RECEIVER = new Receiver()

// Create Commands
const COMMAND1 = new Command1(RECEIVER)
const COMMAND2 = new Command2(RECEIVER)

// Register the commands with the invoker
const INVOKER = new Invoker()
INVOKER.register('1', COMMAND1)
INVOKER.register('2', COMMAND2)

// Execute the commands that are registered on the Invoker
INVOKER.execute('1')
INVOKER.execute('2')
INVOKER.execute('1')
INVOKER.execute('2')