Imagine a list of items:
const data = [0, 1, 2, 3, 4, 5]
One variable represents the main item:
const initialIndex = 1;
And the other variable, the number of extra elements that will also be collected behind of the "main item".
const extraCount = 2;
So, if for example, I call the method "algorithm" as follows:
function algorithm(data, initialIndex, extraCount) { ... }
console.log(algorithm(data, 2, 1));
It will return me [1, 2] // The initial index and the first element behind it
Or, if for example I call again with
console.log(algorithm(data, 4, 3));
It will return me [1, 2, 3, 4] // The initial element and 3 items behind it
How can I do, in a simple way, to fix this use case
console.log(algorithm(data, 1, 2)); // Negative index...
But... I need to return at least the possible items.
I mean:
For console.log(algorithm(data, 1, 2)); I get [0, 1] // Initial index, and the first item before (not two because the second one has a negative index)
For console.log(algorithm(data, 2, 5)); I get [0, 1, 2]
For console.log(algorithm(data, 0, 10)); I get [0]
For console.log(algorithm(data, 3, 7)); I get [0, 1, 2, 3]
This is what I have tried
const data = [0, 1, 2, 3, 4];
const initialIndex = 2;
const extraCount = 2;
const start = initialIndex - extraCount >= 0 ? initialIndex - extraCount : initialIndex;
const end = initialIndex + 1;
console.log(data.slice(start, end));You have it correct. Just replace initialIndex by 0 in else condition
const data = [0, 1, 2, 3, 4];
let func = (initialIndex,extraCount) => {
const start = initialIndex - extraCount >= 0 ? initialIndex - extraCount : 0;
const end = initialIndex + 1;
console.log(data.slice(start, end));
};
func(2,2);
func(1,2);
func(3,7);Note: There are a lot of other ways to do it, but this is the one you were going for so I just pointed out the issue
You can use slice(-count) to return elements from the end of array, something like this:
if (extraCount > initialIndex) {
return [
// This will return elemnts from beginning of array up to initialIndex
...data.slice(0, initialIndex),
// This will return the missing elements looped from the other side of array
...data.slice(extraCount - initialIndex)
];
}
You should also incorporate other sanity checks into your code, or example, total number of elements should not exceed array length, etc.