## JavaScript program to find the sum of all even numbers below a given number:

In this *JavaScript* program, we will learn how to find the sum of all *even* numbers from *1* to that number. We will use a loop to iterate through the numbers from *1 to that number* and for each number, we will check if it is even by using a separate function. If it is *even*, we will add it to a separate variable that will hold the *sum*. Finally, it will print the *sum*.

### Method 1: By using a for loop:

Below is the complete JavaScript program:

```
function isEven(n) {
return n % 2 == 0;
}
function findSum(no) {
let sum = 0;
for (var i = 1; i <= no; i++) {
if (isEven(i)) {
sum += i;
}
}
return sum;
}
console.log(findSum(100));
```

Here,

*isEven*method is used to check if a number is*even*or not. It checks if the number is perfectly divisible by*2*.- The
*findSum*method takes the number as parameter and finds the sum of all*even*numbers from*1*to that*number*. - It uses one
*for loop*that runs from*1 to no*and for each number it checks if it is*even*or not. If it is*even*, it is adding that value to*sum*.*sum*is initialized as*0*. So, once the for loop ends, it will hold the total*sum*of all even numbers in this range.

If I execute the above program, it will give the below output:

`2550`

### Method 2: By using a while loop:

We can also use a *while loop* to solve it. The below program does that:

```
function isEven(n) {
return n % 2 == 0;
}
function findSum(no) {
let sum = 0;
let i = 1;
while (i <= no) {
if (isEven(i)) {
sum += i;
}
i++;
}
return sum;
}
console.log(findSum(100));
```

- It is similar to the above program.
- The difference is that we are using a
*while*loop. It runs from*i=1*to*i=no*. - It is working similar to the for loop.