format phone number

phonetic.spec.ts

import {Phonetic} from './phonetic';

describe('convert phone number to local number', () => {
  const phonetic = new Phonetic('62');
  test('international code with plus', () => {
    expect(phonetic.localize('+628123')).toEqual('08123');
  });

  test('international code with plus and leading zero', () => {
    expect(phonetic.localize('+6208123')).toEqual('08123');
  });

  test('international code with plus and leading zeroes', () => {
    expect(phonetic.localize('+62000000008123')).toEqual('08123');
  });

  test('international to local', () => {
    expect(phonetic.localize('628123')).toEqual('08123');
  });

  test('international code with leading zeroes to local', () => {
    expect(phonetic.localize('62000000008123')).toEqual('08123');
  });
});

describe('convert phone number to international number', () => {
  const phonetic = new Phonetic('62');
  test('normal local number', () => {
    expect(phonetic.internationalize('08123')).toEqual('628123');
  });

  test('number with no zero', () => {
    expect(phonetic.internationalize('8123')).toEqual('628123');
  });

  test('number with same prefix', () => {
    expect(phonetic.internationalize('628123')).toEqual('628123');
  });

  test('leading zeroes', () => {
    expect(phonetic.internationalize('00008123')).toEqual('628123');
  });
});

phonetic.ts

export class Phonetic {
  private plainPrefix: string;

  constructor(private prefix: string) {
    this.plainPrefix = this.numberize(prefix);
  }

  private numberize(phone: string) {
    return phone.replace(/\D+/g, '');
  }

  localize(phone: string) {
    const ph = this.numberize(phone);

    if (!ph || ph.startsWith('0')) {
      return ph;
    }
    const matcher = new RegExp(`^${this.plainPrefix}(?:0+(?=[1-9])|0+(?=0$))?`);
    return ph.replace(matcher, '0');
  }

  internationalize(phone: string) {
    let ph = this.numberize(phone);

    if (!ph || ph.startsWith(this.plainPrefix)) {
      return ph;
    }

    if (ph.startsWith('0')) {
      return ph.replace(/^0+/, this.plainPrefix);
    }

    return this.plainPrefix + ph;
  }
}