dupontL1

See the Pen querySelector by dupont (@dupontcodepen) on CodePen.

const students = document.querySelectorAll("p");

let sum = 0;

let count = 0;

for (const student of students) {

  const mark = Number(student.dataset.mark);

  if (!isNaN(mark)) {

    sum += mark;

    count++;

  }

}

const average = count > 0 ? (value / count).toFixed(2) : "0.00";

// utilisez le bon selector

const elements = document.querySelectorAll("[data-mark]");

let sum = 0;

let count = 0;

for (const el of elements) {

  const mark = Number(el.dataset.mark);

  if (!isNaN(mark)) {

    sum += mark;

    count++;

  }

}

const average = count

  ? (sum / count).toFixed(2)

  : "Aucune note";

// utilisation des méthodes en L2

const marks = [...document.querySelectorAll("[data-mark]")]

  .map(p => Number(p.dataset.mark));

const average =

  marks.length ? (marks.reduce((a, b) => a + b) / marks.length).toFixed(2) : "Aucune note";