Determining beautiful number string in JavaScript

A numeric string, str, is called a beautiful string if it can be split into a sequence arr of two or more positive integers, satisfying the following conditions −

• arr[i] - arr[i - 1] = 1, for any i in the index of sequence, i.e., each element in the sequence is more than the previous element.

• No element of the sequence should contain a leading zero. For example, we can split '50607' into the sequence [5, 06, 07], but it is not beautiful because 06 and 07 have leading zeros.

• The contents of the sequence cannot be rearranged.

For example −

If the input string is −

const str = '91011';

Then the output should be −

const output = true;

because the desired sequence is [9, 10, 11];

Example

The code for this will be −

const str = '91011';
const isBeautiful = (str) => {
   let i = 1;
   let count=0;
   const { length } = str;
   while(i <= length / 2){
      let check = true;
      let j = i;
      let left = BigInt(str.substring(0,j));
      let nextRange = (left + 1n).toString().length;
      while(j + nextRange <= length){
         let right=BigInt(str.substring(j,j+nextRange));
         if(left === right-1n){
            left=right;
            j+=nextRange;
            nextRange=(left+1n).toString().length;
            count=j;
         }else{
            check=false;
            break;
         }
      };
      if(check === true && count === length){
         return true;
      }
      i++;
   };
   return false;
};
console.log(isBeautiful(str));

Output

And the output in the console will be −

true