String interpolation

interpolate.test.ts

import interpolate from './interpolate';

describe('Interpolate for Translations', () => {
  // eslint-disable-next-line jest/no-commented-out-tests
  //   it('blah', () => {
  //     expect(interpolate('asdf')).toEqual('asdf');
  //     expect(interpolate('Hello {0}', ['World!'])).toEqual('Hello World!');
  //     expect(interpolate('Hello {0} {0}', ['World!'])).toEqual('Hello World! World!');
  //     expect(interpolate('Hello {0} {1} {2}!', ['World!', 'Welcome', 'here'])).toEqual('Hello World! Welcome here!');
  //     expect(interpolate('Hello {0} {1} {2}! {1} {2}!', ['World!', 'Welcome', 'here'])).toEqual(
  //       'Hello World! Welcome here! Welcome here!',
  //     );
  //     expect(interpolate('Hello {name}!', { name: 'Adam' })).toEqual('Hello Adam!');
  //     expect(interpolate('Hello {name} {name}!', { name: 'Adam' })).toEqual('Hello Adam Adam!');
  //     expect(interpolate('Hello {name}! Welcome {location}!', { name: 'Adam', location: 'here' })).toEqual(
  //       'Hello Adam! Welcome here!',
  //     );
  //   });

  it('blah', () => {
    expect(interpolate('asdf')).toEqual('asdf');
    expect(interpolate('Hello {0}', 'World!')).toEqual('Hello World!');
    expect(interpolate('Hello {0} {0}', 'World!')).toEqual('Hello World! World!');
    expect(interpolate('Hello {0} {1} {2}!', 'World!', 'Welcome', 'here')).toEqual('Hello World! Welcome here!');
    expect(interpolate('Hello {0} {1} {2}! {1} {2}!', 'World!', 'Welcome', 'here')).toEqual(
      'Hello World! Welcome here! Welcome here!',
    );
    expect(interpolate('Hello {name}!', { name: 'Adam' })).toEqual('Hello Adam!');
    expect(interpolate('Hello {name} {name}!', { name: 'Adam' })).toEqual('Hello Adam Adam!');
    expect(interpolate('Hello {name}! Welcome {location}!', { name: 'Adam', location: 'here' })).toEqual(
      'Hello Adam! Welcome here!',
    );
  });
});

interpolate.ts

function interpolate(str: string, ...args: [Record<string, string | number>] | Array<string | number>): string {
  if (args.length === 0) {
    return str;
  }

  if (args.length === 1 && typeof args[0] === 'object') {
    const obj = args[0] as Record<string, string | number>;

    return Object.keys(obj).reduce((acc, current) => {
      return acc.replace(new RegExp(`\\{${current}\\}`, 'g'), `${obj[current]}`);
    }, str);
  }

  const values = args as Array<string | number>;

  return values.reduce((acc: string, current, idx) => {
    return acc.replace(new RegExp(`\\{${idx}\\}`, 'g'), `${current}`);
  }, str);
}

export default interpolate;