SOURCE

const stats=(function(){
    const sum=(x,y)=>x+y;
    const square=x=>x*x;
    function mean(data){
        return data.reduce(sum)/data.length;
    }
    function stddev(data){
        let m=mean(data);
        return Math.sqrt(
            data.map(x=>x-m).map(square).reduce(sum)/(data.length -1)
        )
    }
})();