class Cmd0 {

  constructor(name, arg1, arg2 = null) {

    this.name = name;

    this.arg1 = arg1;

    this.arg2 = arg2;

  }

// . . .

}

​

class Cmd extends Cmd0 {

  constructor(name, arg1, arg2 = null) {

    myMap =  new.target.getMyMap() // defined in sub-classes

    if (!myMap.has(name)) { super(null, null, null); return } // fail the constructor

    super(name, arg1, arg2)

  }

  getMyMap() {

    return new Map(); // to be overridden or extended in the subclasses

  }

}

​

class SubCmd1 extends Cmd {

  getMyMap() {

    return new Map()

      .set("name11", "arg11, arg12")

      .set("name12", "arg21, arg22")

  }

  Usage() {

    if (this.name) return null

    else return "cmd sub1 bla bla bla"

  }

}

​

class SubCmd2 extends Cmd {

​

  Usage() {

    if (this.name) return null

    else return "cmd sub2 bla bla bla"

  }

}

​

const cli = new SubCmd1("name11", "argsObj") 

const usage = cli.Usage() 

if (usage) { console.log(`Usage:\n\n${usage}`) }

else { console.log(`Valid name ${cli.name}`) }

​

​