你就快完成了。在计算中使用数字，在显示中使用字符串：

const WEEK_DAYS = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
const daysElements = document.querySelectorAll("span.font-light");  // dom elements
const date = new Date();
const today = date.getDay();  // date.getDay() returns a number: 0 for sunday, 1 for monday ... 6 for Saturday

daysElements.forEach((d, index) => d.innerText = WEEK_DAYS[(today + index) % 7]);

span.font-light {display:block}

<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>

这里也可以使用forEach。

你需要使用document.createElement()创建你想要显示的DOM节点。在这个例子中，我使用了一个简单的无序列表。获取父元素（例如使用querySelector()）并使用replaceChildren()将子元素附加到它，然后显示节点。

const weekdays = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
const temperaturesInDegreeCelcius = [21, 23, 19, 10, 18, 25, 24];

const list = document.querySelector(".list");
const listItems = weekdays.map((day, i) => createListItem(day, temperaturesInDegreeCelcius[i]));
list.replaceChildren(...listItems);

function createListItem(day, temperature){
  const li = document.createElement("li");
  li.innerText = `${day}: ${temperature} °C`;
  return li;
}

<ul class="list">
</ul>

很好的答案。我想我会把我的作为一个类似C的for循环的例子。

let daysOfWeek = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
const date = new Date();
d = date.getDay();
l = daysOfWeek.length;
const daysElements = document.querySelectorAll("span.font-light");

for (let i = 0; i < 5; i++) {
  daysElements[i].innerText = daysOfWeek[d % l];
  d++;
}

span.font-light {display:block}

<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>
<span class="font-light"></span>