joinWithConjunction

gistfile1.txt

joinWithConjunction(arr, delimiter, conjunction = 'and', useOxfordComma = true) {
  switch (arr.length) {
    case 0:
    case 1:
      // Use join behavior for these
      return arr.join(delimiter);
    case 2:
      return arr.join(` ${conjunction} `);
    default:
      // We don't use a space between the two to make it work like String.join()
      conjunction = useOxfordComma
        ? `${delimiter}${conjunction}`
        : ` ${conjunction}`;
      return `${arr.slice(0, -1).join(delimiter)}${conjunction} ${arr.slice(-1)}`;
  }
}
  
/* ------------ MOCHA UNIT TESTS ------------- */
  
describe('.joinWithConjunction', () => {
  it('should return the only element if there is only one element', () => {
    expect(joinWithConjunction(['A'], ', ')).to.equal('A');
  });
  it('should return the two elements joined with the conjunction and no delimiter if there are exactly two elements', () => {
    expect(joinWithConjunction(['A', 'B'], ', ', 'or')).to.equal('A or B');
  });
  it('should return all elements joined with the conjunction and delimiter if there are more than two elements', () => {
    expect(joinWithConjunction(['A', 'B', 'C'], ', ', 'or')).to.equal('A, B, or C');
  });
  it('should return all elements joined with the conjunction and delimiter with no last comma if the Oxford comma parameter is false', () => {
    expect(joinWithConjunction(['A', 'B', 'C'], ', ', 'or', false)).to.equal('A, B or C');
  });
  it('should return all elements joined with the default conjunction if not passed in', () => {
    expect(joinWithConjunction(['A', 'B', 'C'], ', ')).to.equal('A, B, and C');
  });
});