Javascript. if else if else confusion

Why the else if condition still executes when the if condition is already true? I thought if the if condition is true anything under it like else if...else or else will be worthless. code:

for (i = 1; i <= 20; i++)
{
    if (i % 3 === 0 && i % 5 === 0)
    {
        console.log("FizzBuzz");
    }
    else if (i % 3 === 0)
    {
        console.log("Fizz");
    }
    else if (i % 5 === 0)
    {
        console.log("Buzz");
    }
    else
    {
        console.log(i);
    }
}

this is the output

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz