let s = (()=>{
    let sum = (arr)=>arr.reduce((a,b)=> a+b);
    let min = (arr) => Math.min(...arr);
    let max = (arr) => Math.max(...arr);
    let product = (arr) => arr.reduce((a,b)=> a*b);
    let join = (arr)=> arr.join('');
    return {sum,min,max,product,join}

})();