Prefer using Array.at when indexing from the end of an array

When accessing items in an array from the end, like the last item, prefer using Array.at with a negative index because it is less error-prone. Note that using Array.at with a positive index is equivalent to indexing into the array normally, and if Array.at references a non-existing index, it will return undefined.

Examples

Incorrect Examples

const items = [1, 2, 3, 4, 5, 6, 7]
const lastItem = items[items.length - 1]

Correct Examples

const items = [1, 2, 3, 4, 5, 6, 7]
const lastItem = items.at(-1)

const items = [1, 2, 3, 4, 5, 6, 7]
 
// This example is fine because it uses a normal, positive index
const firstItem = items[0]

const items = [1, 2, 3, 4, 5, 6, 7]
const index = example()
 
// This example is fine because it uses a variable index
const item = items[index]

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