let firstCard = 10; let secondCard = 4; let sum = firstCard + secondCard; let hasBlackJack = false; let isAlive = true; let message = "" let messageEl = document.getElementById("message-el"); let sumEl = document.querySelector("#sum-el"); let cardsEl = document.getElementById("cards-el"); messageEl.textContent = "Do you want to draw a new card?"; function startGame() { cardsEl.textContent = "Cards : " + firstCard + " " + secondCard; sumEl.textContent = "Sum :" + sum; if (sum <= 20) { message = "Do you want to draw a new card?"; } else if (sum === 21) { message = "You have got blackjack!"; hasBlackJack = ture; } else { message = "You are out of the game!"; isAlive = false; } messageEl.textContent = message; }
这一行：
let messageEl = document.getElementById("message-el");没有返回元素。
这是因为在代码执行时，该元素在 DOM 中不存在。这可能是因为您没有任何具有该 ID 的元素，或者因为您需要在将该元素解析到 DOM 后移动代码来执行。