Get page numbering for booklet printing

makePamphlet.js

const makePamphlet = (suspectInput) => {
    const input = Boolean(suspectInput % 2) ? suspectInput + 1 : suspectInput;
    const evenPages = [
        ...Array(input / 2)
            .fill(0)
            .map((_el, idx) => (idx + 1) * 2),
    ].reverse();
    const oddPages = [
        ...Array(input)
            .fill(0)
            .map((_el, idx) => idx % 2 && idx)
            .filter((e) => e),
    ];
    return [
        ...Array(input/2)
            .fill(0)
            .map((_el, idx) => {
                const output = (Boolean(idx%2))
                    ? [`${evenPages.pop()}`, `${oddPages.pop()}`] // second [2, 15]
                    : [`${evenPages.shift()}`, `${oddPages.shift()}`] // first [16,1]                
                return output
            })
    ].flatMap(p => p).map(n => parseInt(n));
};