Insert into array in reverse while iterating forward

Question

So currently I have this function:

function loadPath(chunkSize, dataSize, depth, index) {
 let path = []
 let i = 0
 while (i < depth) {
 path.unshift(index % chunkSize)
 index = Math.floor(index / chunkSize)
 i++
 }
 return path
}

I would now like to pass in path as a variable from an object pool of short path arrays. So for example:

function loadPath(path, chunkSize, dataSize, depth, index) {
 
}
let path = new Array(3)
loadPath(path, 5, 100, 3, 41)
console.log(path) // 1, 3, 1
loadPath(path, 5, 100, 3, 50)
console.log(path) // ...

The question is, how can I do that without using push/unshift or reverse operations on the array? Basically just treating the array as a static block of memory, while at the same time not adding any unnecessary operations.

function loadPath(path, chunkSize, dataSize, depth, index) {
 let i = 0
 let x = depth - 1
 while (i < depth) {
 path[x] = index % chunkSize
 index = Math.floor(index / chunkSize)
 i++
 x--
 }
}

My question is, can this be done with any fewer temp variables? Some magic along the lines of this?

function loadPath(path, chunkSize, dataSize, depth, index) {
 let i = 0
 while (i < depth) {
 // something tricky perhaps here?
 // since x and i have a reciprocal relationship...
 // somehow fill it in backwards...
 path[depth - i] = index % chunkSize
 index = Math.floor(index / chunkSize)
 i++
 }
}

Or perhaps there is another way entirely to write this algorithm to be in as few steps and operations and temp variables as possible.

Could also use this floor implementation integrated somehow if it helps :)

function floor(n) {
 return ~~n - (~~n > n)
}

• FreezePhoenix: Your title short be short and concise while explaining what your code does.
• RoToRa: You should be able to calculate the number of loops you need to do, so you can create an empty array of that size and fill it backwards. If I'm not mistaken it should be Math.log(chunkSize) / Math.log(index) (rounded up).
• iAmOren: Would you consider using concat?
• iAmOren: How about: path[depth - i - 1] = index % chunkSize - no need for x.
• iAmOren: What is this mysterious index and what is/why are you not using dataSize?

Answer 1

Let's try the other way:

function loadPath(path, chunkSize, dataSize, depth, index) {
 for(var i = 0; i < depth; i++) {
 path[depth - i - 1] = index % chunkSize;
 index = Math.floor(index / chunkSize);
 };
};
var path = Array(3);
console.log("loadPath(path, 5, 100, 3, 41)");
loadPath(path, 5, 100, 3, 41);
console.log(path);
console.log("loadPath(path, 5, 100, 3, 50)");
loadPath(path, 5, 100, 3, 50);
console.log(path);

.as-console-wrapper { max-height: 100% !important; top: 0; }

What do you want to do if index >= chunkSize^3?

• iAmOren: Thank you for the accept! Up-vote, please?!? :) Still: What do you want to do if index >= chunkSize^3?
• Lance Pollard: I can handle that outside of the function no problem.
• iAmOren: Great! Thanks for the up-vote. I still have no clue as to what you are doing... :)
• Lance Pollard: I am working on a vm and this is an aspect of the memory allocation part.
• Sᴀᴍ Onᴇᴌᴀ: Without a declaration for i using var or let a global variable would be created, which won't lead to an error but typically frowned upon

Answer 2

Same Answer to your own same/similar Question...
Hint: accept and up-vote both... :)

function recBucket(number, size) {
 if(number<size) return [number];
 else {
 var whole=Math.floor(number/size);
 return [recBucket(whole, size), number-whole*size].flat();
 }
};
function loadPath(chunkSize, dataSize, depth, index) {
 return recBucket(index, chunkSize);
};
console.log(loadPath(5, 100, 3, 41));
console.log(loadPath(5, 100, 3, 50));

.as-console-wrapper { max-height: 100% !important; top: 0; }

• Lance Pollard: .flat feels a feels a bit hacky, just hiding implementation details to make things appear shorter.
• Lance Pollard: Also recursion is less-than ideal.