[3] 无重复字符的最长子串

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function (s) {
  let max = 0;
  let num = 0;
  let hasp;
  const hashMap = new Map()
  for (let i = 0; i < s.length; i++) {
    hasp = s.charAt(i);
    if (hashMap.get(hasp) || hashMap.get(hasp) === 0) {
      num = Math.max(num, hashMap.get(hasp) + 1);
    }
    max = Math.max(max, i - num + 1);
    hashMap.set(hasp, i)
  }
  return max;

}