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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 −
harshadNum(1014) = harshadNum(1015) = harshadNum(1016) = harshadNum(1017) = 4 harshadNum(1) = 10 harshadNum(12) = 1 harshadNum(23) = -1
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.
Coding the isHarshad function() −
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
if(!isHarshad(number)){
return -1;
}
let streak = 1, prev = number-1, next = number+1;
//check preceding streak
while(isHarshad(prev) && prev > 0){
streak++;
prev--;
}
//check succeeding streak
while(isHarshad(next)){
streak++;
next++;
}
return streak;
};
console.log(harshadNum(1014));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
if(!isHarshad(number)){
return -1;
}
let streak = 1, prev = number-1, next = number+1;
//check preceding streak
while(isHarshad(prev) && prev > 0){
streak++;
prev--;
}
//check succeeding streak
while(isHarshad(next)){
streak++;
next++;
}
return streak;
};
console.log(harshadNum(1014));Output
Output for this code in the console will be −
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