required_args.js

'use strict';

// none of this is good

class Greet {
  required(arg) {
    throw new Error(`${arg} is required`);
  }

  requireArgs(given, required) {
    for (let i=0; i<required.length; i++) {
      if (!given[i]) {
        throw new Error(`${required[i]} is required`);
      }
    }
    return given.slice(0, required.length);
  }

  // easy, but verbose declaration of named arguments
  hello(name=this.required('name'), color=this.required('color')) {
    console.log(`hello ${name}, nice ${color} heelys`);
  }

  // less easy and clear for no real reason
  hi(...args) {
    const [name, color] = this.requireArgs(args, ['name', 'color']);
    console.log(`hi ${name}, nice ${color} haircut`);
  }
}

const greeter = new Greet();
greeter.hello('Chris', 'murple');
// greeter.hello('Chris'); // throws error
greeter.hi('Chris', 'greue');
// greeter.hi('Chris'); // throws error