JavaScript: Find longest substring in a given string without repeating characters
JavaScript Function: Exercise-26 with Solution
Write a JavaScript function to find longest substring in a given string without repeating characters.
Sample Solution: -
HTML Code:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Find longest substring in a given string without repeating characters</title>
</head>
<body>
</body>
</html>
JavaScript Code:
function longest_substring_without_repeating_characters(input) {
var chars = input.split('');
var curr_char;
var str = "";
var longest_string = "";
var hash = {};
for (var i = 0; i < chars.length; i++) {
curr_char = chars[i];
if (!hash[chars[i]])
{
str += curr_char;
hash[chars[i]] = {index:i};
}
else
{
if(longest_string.length <= str.length)
{
longest_string = str;
}
var prev_dupeIndex = hash[curr_char].index;
var str_FromPrevDupe = input.substring(prev_dupeIndex + 1, i);
str = str_FromPrevDupe + curr_char;
hash = {};
for (var j = prev_dupeIndex + 1; j <= i; j++) {
hash[input.charAt(j)] = {index:j};
}
}
}
return longest_string.length > str.length ? longest_string : str;
}
console.log(longest_substring_without_repeating_characters("google.com"));
console.log(longest_substring_without_repeating_characters("example.com"));
Output:
gle.com xample.co
Flowchart:

Live Demo:
See the Pen JavaScript - Find longest substring in a given a string without repeating characters-function-ex- 26 by w3resource (@w3resource) on CodePen.
Improve this sample solution and post your code through Disqus
Previous: Write a JavaScript function that accept a list of country names as input and returns the longest country name as output
Next: Write a JavaScript function that returns the longest palindrome in a given string.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.
JavaScript: Tips of the Day
Shorten an array using its length property
A great way of shortening an array is by redefining its length property.
let array = [0, 1, 2, 3, 4, 5, 6, 6, 8, 9] array.length = 4 // Result: [0, 1, 2, 3]
Important to know though is that this is a destructive way of changing the array. This means you lose all the other values that used to be in the array.
Ref: https://bit.ly/2LBj213
- Weekly Trends
- Java Basic Programming Exercises
- SQL Subqueries
- Adventureworks Database Exercises
- C# Sharp Basic Exercises
- SQL COUNT() with distinct
- JavaScript String Exercises
- JavaScript HTML Form Validation
- Java Collection Exercises
- SQL COUNT() function
- SQL Inner Join
- JavaScript functions Exercises
- Python Tutorial
- Python Array Exercises
- SQL Cross Join
- C# Sharp Array Exercises