LeetCode实现strStr() JavaScript解法

/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
var strStr = function(haystack, needle) {
    if(needle === "") return 0;
    let array =  haystack.split(needle);
    if(array.length === 1) return -1;
    return array[0].length
};