Formatar número de telefone

format-phone-number.spec.ts

import { formatPhoneNumber } from './format-phone-number';

describe('formatPhoneNumber', () => {
  it('deve formatar como XXXX-XXXX se tiver 8 dígitos', () => {
    expect(formatPhoneNumber('12345678')).toEqual('1234-5678');
  });

  it('deve formatar como X XXXX-XXXX se tiver 9 dígitos', () => {
    expect(formatPhoneNumber('912345678')).toEqual('9 1234-5678');
  });

  it('deve formatar como (XX) XXXX-XXXX se tiver 10 dígitos', () => {
    expect(formatPhoneNumber('7912345678')).toEqual('(79) 1234-5678');
  });

  it('deve formatar como (XX) X XXXX-XXXX se tiver 11 dígitos', () => {
    expect(formatPhoneNumber('79912345678')).toEqual('(79) 9 1234-5678');
  });

  it('deve formatar como +XX (XX) XXXX-XXXX se tiver 12 dígitos', () => {
    expect(formatPhoneNumber('557912345678')).toEqual('+55 (79) 1234-5678');
  });

  it('deve formatar como +XX (XX) X XXXX-XXXX se tiver 13 dígitos', () => {
    expect(formatPhoneNumber('5579912345678')).toEqual('+55 (79) 9 1234-5678');
  });
});

format-phone-number.ts

export const formatPhoneNumber = (value: string) => {
  const CODIGO_PAIS = 2;
  const DDD = 2;
  const DIGITO_OPCIONAL = 1;
  const NUMERO = 8;

  const replacers: Record<number, [RegExp, string]> = {
    [NUMERO]: [/(\d{4})(\d{4})/, '$1-$2'],
    [DIGITO_OPCIONAL + NUMERO]: [/(\d{1})(\d{4})(\d{4})/, '$1 $2-$3'],
    [DDD + NUMERO]: [/(\d{2})(\d{4})(\d{4})/, '($1) $2-$3'],
    [DDD + DIGITO_OPCIONAL + NUMERO]: [
      /(\d{2})(\d{1})(\d{4})(\d{4})/,
      '($1) $2 $3-$4',
    ],
    [CODIGO_PAIS + DDD + NUMERO]: [
      /(\d{2})(\d{2})(\d{4})(\d{4})/,
      '+$1 ($2) $3-$4',
    ],
    [CODIGO_PAIS + DDD + DIGITO_OPCIONAL + NUMERO]: [
      /(\d{2})(\d{2})(\d{1})(\d{4})(\d{4})/,
      '+$1 ($2) $3 $4-$5',
    ],
  };

  const [regEx, matcher] = replacers[value.length];

  if (regEx && matcher) {
    return value.replace(regEx, matcher);
  }

  return value;
};