# Finding out the Harshad number JavaScript

Harshad numbers are those numbers which are exactly divisible by the sum of their digits. Like the number 126, it is completely divisible by 1+2+6 = 9.

• All single digit numbers are harshad numbers.

• Harshad numbers often exist in consecutive clusters like [1,2,3,4,5,6,7,8,9,10], [110,111,112], [1010, 1011, 1012].

Our job is to write a function that takes in a Number as input checks whether it’s a harshad number or not, if not then returns -1 otherwise it returns the length of streak of consecutive harshad cluster.

For example −

Let’s break this problem into two major functions,

• isHarshad() →  takes in a number num and returns a boolean depending upon whether the number is harshad or not.

• harshadNum() → main function that takes in the actual number, makes call to isHarshad() at various points and returns the length of streak.

const isHarshad = (num) => {
let sum = 0, temp = num;
while(temp){
sum += temp % 10;
temp = Math.floor(temp/10);
}
return num % sum === 0;
}

Pretty simple iterative function that returns a boolean

Now let’s code the harshadNum() function −

const harshadNum = (number) => {
//if the input is not harshad return -1
return -1;
}
let streak = 1, prev = number-1, next = number+1;
//check preceding streak
streak++;
prev--;
}
//check succeeding streak
streak++;
next++;
}
return streak;
};

Understanding the above code −

• Check whether the input is harshad or not, if not stop the function and return -1;

• Run one loop backwards, one forwards while we keep getting harshad numbers,simultaneously keep updating the streak

• Lastly return the streak

Following is the complete code −

## Example

const isHarshad = (num) => {
let sum = 0, temp = num;
while(temp){
sum += temp % 10;
temp = Math.floor(temp/10);
}
return num % sum === 0;
}
const harshadNum = (number) => {
//if the input is not harshad return -1
return -1;
}
let streak = 1, prev = number-1, next = number+1;
//check preceding streak
streak++;
prev--;
}
//check succeeding streak
streak++;
next++;
}
return streak;
};