text: export function strStr(haystack, needle) {
    const haystackLen = haystack.length;
    const needleLen = needle.length;
  
    for (let i = 0; i <= haystackLen - needleLen; i++) {
      if (haystack.substring(i, i + needleLen) === needle) {
        return i;
      }
    }
  
    return -1;
  }
  