added more solution approach with well comments to understand

[AnishMandal939]

// So we have two methods to one by creating extra space annd without creating extra space // with extra spaces let uniqueChars = (str) =>{ // creating a empty variable to map let characters = {}; // iterate through all characters of the string and start inserting them one by one characters tabole for(var i = 0; i < str.length; i++){ // check if string already present in characters variable if(characters[str[i]] != null) { // if present repetation of character than return false characters[str[i]] = 1; return false; }else{ // !present duplicate characters than return true characters[str[i]] = 0;

  }

  }
  return true;

} // Since we are iterating trough each element of string only once string of length 1 average and worst case time complexity is O(n) // without extra spaces

let uniqueChar = (str) => { // iterate through string for(let i =0; i< str.length; i++){ // checking against the subsequent characters & iterating through them for(let j = i+1; j <=str.length-1; j++){ if(str[i] == str[j]){ return false; } } } return true; }

/* TESTS */ console.log(everyCharUnique('abcd'), 'true'); console.log(everyCharUnique('abccd'), 'false'); console.log(everyCharUnique('bhjjb'), 'false'); console.log(everyCharUnique('mdjq'), 'true'); console.log(everyCharUniques('mdjq'), 'true'); console.log(uniqueChars('hello'), 'false'); console.log(uniqueChars('anish'), 'true'); console.log(uniqueChar('hello'), 'false'); console.log(uniqueChar('anish'), 'true');