const unrepeated = (str) => [...new Set(str)].join('');

​

unrepeated("hello"); //➞ "helo"

unrepeated("aaaaabbbbbb"); //➞ "ab"

unrepeated("11112222223333!!!??"); //➞ "123!?"

function removeDuplicateCharacters(string) {

  return string

    .split('')

    .filter(function(item, pos, self) {

      return self.indexOf(item) == pos;

    })

    .join('');

}

console.log(removeDuplicateCharacters('baraban'));

function removeDuplicate(str, letSingleChar = false)  {

    let string = str;

    for (element of string) {

        const re = new RegExp(element, 'g');

        if (string.match(re)?.length > 1) {

          if (letSingleChar == true) {

            string = [...new Set(string.split(''))].join('');

          } else 

            string = string.replace(re, '');

        }

    }

    return string;

} 

​

console.log(removeDuplicate("Hello World", true)) // Helo Wrd

console.log(removeDuplicate("Hello World", false )) // He Wrd

const arr = [1, 2, [3, 4]];

​

// To flat single level array

arr.flat();

// is equivalent to

arr.reduce((acc, val) => acc.concat(val), []);

// [1, 2, 3, 4]

​

// or with decomposition syntax

const flattened = arr => [].concat(...arr);

​

const arr = [1, 2, [3, 4]];

​

// To flat single level array

arr.flat();

// is equivalent to

arr.reduce((acc, val) => acc.concat(val), []);

// [1, 2, 3, 4]

​

// or with decomposition syntax

const flattened = arr => [].concat(...arr);

​

const arr = [1, 2, [3, 4]];

​

// To flat single level array

arr.flat();

// is equivalent to

arr.reduce((acc, val) => acc.concat(val), []);

// [1, 2, 3, 4]

​

// or with decomposition syntax

const flattened = arr => [].concat(...arr);

​

const arr = [1, 2, [3, 4]];

​

// To flat single level array

arr.flat();

// is equivalent to

arr.reduce((acc, val) => acc.concat(val), []);

// [1, 2, 3, 4]

​

// or with decomposition syntax

const flattened = arr => [].concat(...arr);

​

const arr = [1, 2, [3, 4]];

​

// To flat single level array

arr.flat();

// is equivalent to

arr.reduce((acc, val) => acc.concat(val), []);

// [1, 2, 3, 4]

​

// or with decomposition syntax

const flattened = arr => [].concat(...arr);

​