SOURCE

function quick(arr) {
    if(arr.length<=1){
        return arr
    }

    let a =  Math.round(arr.length/2)
    let piv = arr[a]
    let left = arr.filter(x => x < piv)
    let mids = arr.filter(x => x == piv)
    let right = arr.filter(x => x > piv)
    
    // return quick(left).concat(mids, quick(right))
    return [...quick(left), ...mids, ...quick(right)]
}

console.log(quick([3,5,1,3,4,5,6,7,8,8,5,9,8,3]))