JavaScript 四捨五入とかとか

切り捨てとか四捨五入とかとか
Math.floor() - JavaScript | MDN
Number.prototype.toFixed() - JavaScript | MDN

'use strict';

{
    const scores = [10,3,9];
    let sum = 0;
    scores.forEach(score => {
        sum += score;
    });

    const avg = sum / scores.length;
    console.log(sum); // 22
    console.log(avg); // 7.333333333333333

    console.log(Math.floor(avg)); // 7 (切り捨て)
    console.log(Math.ceil(avg)); // 8 (切り上げ)
    console.log(Math.round(avg)); // 7 (四捨五入)
    console.log(avg.toFixed(3)); // 7.333 (指定桁)
}