Question

我最近开始学习JS，在做我的第一个项目时遇到了问题。控制台显示未定义变量billAm。我不确定为什么已经定义了变量，为什么会这样？

下面的代码段：

function calculateTip() {
  let billAm = document.getElementById("billam").value;
  let serviceQual = document.getElementById("quality").value;
}

if (billAm === "" || serviceQual == 0) {
  alert("Please enter values");
}

let total = (billAm * serviceQual);
total = Math.round(total * 100) / 100;
total = total.toFixed(2);
document.getElementById("total").style.display = "block";
document.getElementById("tip").innerHTML = total;



document.getElementById("total").style.display = "none";

document.getElementById("calculate").onclick = function() {
  calculateTip();

};

<div id="background">
  <h3 class="headline">
    Tip calculator
  </h3>
  <input type=text id="billam" placeholder="Amount">
  <h3 class="review">
    How was your service?
  </h3>
  <select id="quality">
    <option disabled selected value="0">How was Your Experience?</option>
    <option value="0.3">30&#37; &#45; Outstanding</option>
    <option value="0.2">20&#37; &#45; Good</option>
    <option value="0.15">15&#37; &#45; It was OK</option>
    <option value="0.1">10&#37; &#45; Bad</option>
    <option value="0.05">5&#37; &#45; Terrible</option>
  </select>
  <button type="button" id="calculate">Calculate!</button>
  <div id="total">
    <sup>€</sup><span id="tip">0.00</span>
    <script src="script.js"></script>
  </div>
</div>

Answer 1

因为您已经在函数内部定义了它，所以它的范围仅限于该函数。

您可以参考此答案以获取更多详细信息 https://stackoverflow.com/a/500459/1588446

为什么在控制台中记录了已定义变量但未定义的错误？

1 个答案: