[javascript] 뒤에서부터 문자 찾기 lastIndexOf

function solution1(string) {
  var a = 'an';
  if (string.lastIndexOf(a) == -1) {
    return null;
  } else {
    return string.slice(0, string.lastIndexOf(a) + a.length);
  }
}
function solution2(string) {
  var a = 'an';
  if (string.lastIndexOf(a) == -1) {
    return null;
  } else {
    return string.substring(0, string.lastIndexOf(a) + a.length);
  }
}

const string = [
  'Apple Banana Cat',
  'Car Dance Hat',
  'Chocolate Grammar Mat',
  'Lake Apple Dance',
  'Banana Cat Hat',
  'Chocolate Lake Mat',
  'Car Apple Hat',
  'Dance Lake Mat',
  'Cat Chocolate Dance',
  'Grammar Hat Apple',
];

for (let i = 0; i < string.length; i++) {
  console.log('solution1', solution1(string[i]));
  console.log('solution2', solution2(string[i]));
}