TypeScript implementation of simple adjacent iterator

adjacentPairs.ts

function* adjacentPairs<T>(itr: Iterable<T>, n: number, isClosed: boolean) {
    const first = new Array(n - 1) as T[];
    const buffer = new Array(n) as T[];
    let count = 0;
    for (const value of itr) {
        pull(buffer, value);

        if (++count >= n) {
            yield [...buffer];
        } else if (count < n) {
            first[count - 1] = value;
        }
    }
    if (count >= n && isClosed) {
        for (const value of first) {
            pull(buffer, value);
            yield [...buffer];
        }
    }
}

function pull<T>(values: T[], newValue: T) {
    for (let i = 0; i < values.length - 1; ++i) {
        values[i] = values[i + 1];
    }
    values[values.length - 1] = newValue;
}

Very useful when you're dealing geometric things. Also this is error-free when there is not enough things in your array.

Example

console.log(...adjacentPairs([0, 1, 2], 2, false)) // [0, 1], [1, 2]
console.log(...adjacentPairs([0, 1, 2], 2, true)) // [0, 1], [1, 2], [2, 0]
console.log(...adjacentPairs([0, 1, 2], 3, false)) // [0, 1, 2]
console.log(...adjacentPairs([0, 1, 2], 3, true)) // [0, 1, 2], [1, 2, 0], [2, 0, 1]
console.log(...adjacentPairs([0], 2, true)) // nothing
console.log(...adjacentPairs([], 2, true)) // nothing