Findthe Indexofthe First Occurrenceina String

Find the Index of the First Occurrence in a String Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1: Input: haystack = "sadbutsad", needle = "sad" Output: 0 Explanation: "sad" occurs at index 0 and 6. The first occurrence is at index 0, so we return 0. Example 2: Input: haystack = "leetcode", needle = "leeto" Output: -1 Explanation: "leeto" did not occur in "leetcode", so we return -1. Constraints: 1 <= haystack.length, needle.length <= 104 haystack and needle consist of only lowercase English characters. * @param {string} haystack @param {string} needle @return {number}

var strStr = function (haystack, needle) {
  if (needle === "") {
    return 0;
  }
  if (haystack.length < needle.length) {
    return -1;
  }

  for (let i = 0; i <= haystack.length - needle.length; i++) {
    let match = true;
    for (let j = 0; j < needle.length; j++) {
      if (haystack[i + j] !== needle[j]) {
        match = false;
        break;
      }
    }
    if (match) {
      return i;
    }
  }
  return -1;
};