Inside the if element

JavaScript
1

Write a program that prints the sum of all odd numbers from 1 to 50 using a for loop.

let sum = 0;

for (let num = 1; num <=50; num++) {
  if (num % 2 !== 0) {
    sum += num;
  }
}
console.log(sum);

The “if” elements confuses me. What do they mean? num % 2 !==0.

2

Hi there,

The ‘%’ represents the ‘modulus operator’.

This refers to the remainder left over when a number is divided by another number.

Example 4 % 2 = 0, because when you divide 4 by 2, 2 divides perfectly into 4, leaving no remainder.

In the case of 5 % 2, the answer would be 1, since when you divide 5 by 2, the answer is 2, but with 1 left over - this left over part if the remainder and this equates to the modulus.

This is useful when determining whether a number is odd or even, as the modulus of an even number will always give ‘0’ when divided by 2, but the modulus of an odd number will always give 1 (this would work differently for values such as 0 and 1 obviously…).

In your example !== means ‘no equal to’, so maybe you can now figure out what the code means?

Hope this helps.

3

They are using the remainder operator

when you divide two numbers there will be a remainder

for example 12 /2 is 6
but it has a remainder of 0 because we are dividing two even numbers

but if you have 13/6 you would get 2.16 with a remainder of 1

this expression is used to check if a number is odd

if num is a even number, then the result would be false

for example

12 % 2 !== 0

if num is odd, then result would be true and sum += num would run

for example

11 % 2 !== 0

hope that helps

4

So, divided by 2 but not equal to “0” the modulus of an even number, so it’ll be an odd number.? Yes?

5

Exactly. If, (after being divided by 2), the remainder is 1, it means that the number is odd.

In other words, the condition is checking whether the number is odd or not.

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6

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