namespaces.ts

namespace Validation {
  export interface StringValidator {
    isAcceptable(s: string): boolean;
  }

  const lettersRegexp = /^[A-Za-z]+$/;
  const numberRegexp = /^[0-9]+$/;

  export class LettersOnlyValidator implements StringValidator {
    isAcceptable(s: string) {
      return lettersRegexp.test(s);
    }
  }

  export class ZipCodeValidator implements StringValidator {
    isAcceptable(s: string) {
      return s.length === 5 && numberRegexp.test(s);
    }
  }
}

// Some samples to try
let strings = ['Hello', '98052', '101', 'Prueba'];

// Validators to use
let validators: { [s: string]: Validation.StringValidator } = {};
validators['ZIP code'] = new Validation.ZipCodeValidator();
validators['Letters only'] = new Validation.LettersOnlyValidator();

// Show whether each string passed each validator
for (let s of strings) {
  for (let name in validators) {
    console.log(
      `"${s}" - ${
        validators[name].isAcceptable(s) ? 'matches' : 'does not match'
      } ${name}`,
    );
  }
}