String questions

`Array.prototype.join` joins all elements of an array into a string separated by a specified separator. The default separator is a comma. 

const arr = ['a', 'b', 'c'];
const joined = arr.join('-');
console.log(joined); // 'a-b-c'

`Array.prototype.toLocaleString` returns a string representing the array and its elements, formatted according to the locale and options. It uses the `toLocaleString` method of each element. 

const arr = [1, 2, 3];
console.log(arr.toLocaleString()); // '1,2,3' (may vary depending on locale)

`String.prototype.split` splits a string into an array of substrings based on a specified separator. The separator can be a string or regular expression. 

const str = 'a,b,c';
const arr = str.split(',');
console.log(arr); // ['a', 'b', 'c']

`String.prototype.repeat` returns a new string with the specified number of copies of the original string, concatenated together. 

const str = 'abc';
const repeated = str.repeat(3);
console.log(repeated); // 'abcabcabc'

`String.prototype.toLowerCase` returns a new string with all characters converted to lowercase. 

const str = 'HELLO';
const lower = str.toLowerCase();
console.log(lower); // 'hello'

`String.prototype.bold` returns a string wrapped in HTML `<b>` tags. Note that this method is deprecated and should not be used in modern applications. 

const str = 'hello';
const boldStr = str.bold();
console.log(boldStr); // '<b>hello</b>'

Use a sliding window and hash maps to compare character counts. Slide the window across the string and check if the counts match. For example, in 'cbaebabacd' with pattern 'abc', the start indices of anagrams are 0 and 6.

Use a dynamic programming approach to build a table that tracks palindromic substrings. For example, in 'babad', the longest palindromic substring is 'bab' or 'aba'.

Use dynamic programming to build a table where each cell represents the length of the longest common subsequence up to those indices. For example, for 'abcde' and 'aceb', the longest common subsequence is 'ace' with length 3.

Use a hash map to count the frequency of each character, then iterate through the string to find the first character with a count of 1. For example, in 'swiss', the first non-repeating character is 'w'.