Write a function that takes a number as input and returns sum from 1 to n. For example, if the input is 10, the function should return 55.
Write a function called getNaturalSum that takes a number n as its parameter and returns sum of natural number.
// Function that calculates the sum of n natural number.
function getNaturalSum(n) {
let sum = 0; // Declare a sum variable to store the sum
// Running loop from 1 to n
for (let i = 1; i <= n; i++) {
// Adding the sum by i
sum += i; // sum = sum + i;
}
return sum; // Return the sum
}
In the getNaturalSum function, declare sum variable to store the sum and initializing with 0 and then running a loop from 1 to n and adding the sum with all the numbers from 1 to num. After finishing the loop return the sum.
// Function that calculates the sum of n natural number.
function getNaturalSum(n) {
// Using ternary operator (?:)
return n <= 1 ? n : n + getNaturalSum(n - 1);
}
In the getNaturalSum function, checking value of n if n is more than 1 then adding n and return value of getNaturalSum with less than 1 n value. if value is less than or equal to 1 then it will return n, that value, and recursive function will return sum.
Here is example how recursive function calculate factorial of 5:
function getFactorial(num) {
return 5 + getFactorial(4);
4 + getFactorial(3);
3 + getFactorial(2);
2 + getFactorial(1);
return 1;
}