FizzBuzz into array with javascript into an array not working properly

This is my first question so sorry if it’s dumb. I’m trying to do the classic FizzBuzz exercise in the console using javascrypt, putting the changes into an array for 1 to 100. So far:

let nums = [];

for (let i = 1; i <= 100; i++) {
    nums.push(i);
}

for (num of nums) {
    if (nums[num] % 5 === 0) {
        nums[num] = "Buzz";
        console.log("Buzz");
    }
    else if (nums[num] % 3 === 0) {
        nums[num] = "Fizz";
        console.log("Fizz");
    }
    else if (nums[num] % 3 === 0 && nums[num] % 5 === 0) {
        nums[num] = "FizzBuzz";
        console.log("FizzBuzz");
    }
    else {
        console.log(nums[num]);
    }

}

I’m expecting each FizzBuzz to be put into the array instead of the number, and all the array to be printed on the console. But for some specific numbers it doesn’t work. When two vales need to be changed consequently, the second one gives some kind of error. What am i missing?

Thanks for your help!

>Solution :

The issue is that you’re counting starts at 1, and you’re using that number as an index. First entry in the array is nums[0] but you’re using nums[num] where num==1 so you’re getting nums[1] as the first entry.

So first entry is:

num == 1
nums[1] == 2  // as nums[0] == 1

then next

num == 2
nums[2] == 3, so replace with Fizz

now next entry in the array is nums[2] (0,1 above) and nums[2] == Fizz (replaced above)

num == "Fizz"
nums["Fizz"] == undefined

There are two fixes:

1. start at 0
2. use for of

Starting at 0 means your num is the same as the index and you’re not replacing the "next" value with fizz/buzz. The problem is you have to start at 0.

Using for of means you use the indexes directly instead of the values, so the position doesn’t matter – you could for example populate in your initial using with i+=10 instead of i++ to get different values.

for (num of nums) gives the values (1,2,3,"Fizz",…) and would be the same as:

for (let i=0; i<nums.length; ++i) {
    num = nums[i]

(ye-olde method before for of existed)

while for (num in nums) gives the indexes (0,1,2…) and would be the same as

for (let num = 0; num<nums.length; ++num)`

Using for of seems the appropriate solution here.