JSFiddle - React, Tailwind, and code Playground

JavaScript

class Akku {
  constructor(){
    this.total = 0n;
    this.count = 0n;
  }
  get average(){
    return this.total / this.count;
  }
  add(value){
    this.total += BigInt(value);
    this.count += 1n;
  }
  addAll(x){
    for(const v of x)
      this.add(v);
  }
}

const array = new Array(1000).fill(0).map(()=>Math.random()*1000+0.5|0);

const akku = new Akku();
akku.addAll(array);

document.writeln(akku.average);