Array join - Dynamic seperators

// joining arrays with dynamic separators.

// Array::reduce(fn(prev, curr, index, list), initprev)

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10].reduce(function(prev, curr, key) {
    // prev is the joined section. on the first loop it's ''(initprev).
    return prev +
        (key === 0 ?
            '' :
            ['#', '$', '!', '@', '*'][Math.floor(Math.random() * 5)]
        ) +
        curr
}, '')