arrow.js

function arrow(number) {
    const isEven = number % 2 == 0;
    const middles = isEven ? [Math.floor(number / 2) - 1, Math.floor(number / 2)] : [Math.floor(number / 2)]
    const middle = middles[0]
    new Array(number).fill(1).forEach((_, idx) => {
        let indent = 0;
        if (middles.includes(idx)) {
            indent = middle
        } else if (idx < middle) {
            indent = idx
        } else {
            indent = number - 1 - idx
        }
        console.log(`${' '.repeat(indent)}*`)
    })
}