*We will be seeing the solution to the LeetCode problem 3 in JavaScript. I hope you will find it useful.*

**Problem Statement:**

Given a string `s`

, find the length of the **longest substring** without repeating characters.

**Link to Problem**: https://leetcode.com/problems/longest-substring-without-repeating-characters

# JavaScript Implementation:

`var lengthOfLongestSubstring = function(s) {`

let length = s.length

if(s==""){ return 0};

let hashMap = {};

let start = 0;

let sub_sequnce_now = 0;

let max_sub_sequnce_now = 0;

for(let i = 0;i<length;i++){

if(hashMap[s[i]] != null && (start<=hashMap[s[i]])){

sub_sequnce_now = sub_sequnce_now-(hashMap[s[i]] - start);

start = hashMap[s[i]]+1

hashMap[s[i]] = i;

}else{

hashMap[s[i]] = i;

sub_sequnce_now=sub_sequnce_now+1;

if(max_sub_sequnce_now<sub_sequnce_now){

max_sub_sequnce_now = sub_sequnce_now

}

}

}

return max_sub_sequnce_now

};

Thank you for reading hope this code is helpful to you.