JavaScript (sort of) Abstract Class

abstract.js

class EmailProvider {
    #config = {}

    constructor(config) {
        this.#config = config
        if (new.target === EmailProvider) {
            throw new Error('Cannot construct EmailProvider instances directly')
        }

        if (this.send === EmailProvider.prototype.send) {
            throw new Error(`EmailProvider[${new.target.name}]: missing send implementation`)
        }
    }

    send() {
        throw new Error('EmailProvider.send should not be called directly')
    }
}


class Sendgrid extends EmailProvider {
    send(message) {
        console.log('swoosh: ', message)
    }
}

class Mailjet extends EmailProvider {}


const providers = {
    SENDGRID: 'sendgrid',
    MAILJET: 'mailjet',
}
const MailerFactory = (provider, config = {}) => {
    switch (provider) {
        case providers.SENDGRID: return new Sendgrid(config)
        case providers.MAILJET: return new Mailjet(config)
        default: throw new Error('Email provider not implemented')
    }
}

MailerFactory(providers.SENDGRID) // ok
MailerFactory(providers.MAILJET)  // throws
new EmailProvider()				  // throws