Leetcode problem 13 - 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.

/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
var strStr = function (haystack, needle) {
  return haystack.indexOf(needle);
};

Inside the function, it uses the indexOf() method on the haystack string to search for the first occurrence of the needle string. The indexOf() method returns the starting index of the first occurrence of the needle in the haystack. If the needle is not found, it returns -1.