[英]html elements load after Javascript file even though the <script> tag is at the bottom of the <body> tag
我遇到了 Javascript 问题。 HTML 元素一直在等待 javascript 文件，即使脚本标记位于页面底部。 元素不会更新，如果更改并在 5 秒后消失这是代码：
代码：
<!DOCTYPE html>
<html>
<head>
<title>Javascript</title>
<link rel="stylesheet" type="text/css" href="">
</head>
<body>
<h1>javascript in HTML</h1>
<p>HElllllooooo</p>
<script type="text/javascript">
var age = prompt("What is your age?");
if (Number(age) < 18) {
alert("Sorry, you are too young to drive this car. Powering off ");
} else if (Number(age) > 18) {
alert("Powering on. Enjoy the ride!");
} else if (Number(age) === 18 ) {
alert("Congratulations on your first year of driving. Enjoy the
ride!");
}
</script>
</body>
</html>
prompt是同步的，因此阻止执行直到返回。 这就是为什么第二行（以及其余各行）在prompt返回之前不执行的原因。
至于位于底部的script标签，请按以下方式实施：
window.onload = myFunction
您可能需要将其添加到其自己的匿名函数中，该函数可以设置为在onload上运行；
理论上应该可以正常工作：
(function () {
var age = prompt("What is your age?");
if (Number(age) < 18) {
alert("...");
} else if (Number(age) > 18) {
alert("...");
} else if (Number(age) === 18) {
alert("...");
} else {
// ... fallback logic?
}
})();
或者，正如已经回答的那样，您可能需要将代码包装在window.load var中。 也是一个匿名函数。
只需像这样在<body>上添加一个onload属性，无论如何：
<body onload="carsGoBrr()">
然后定义函数：
function carsGoBrr() {
var age = prompt("What is your age?");
if (Number(age) < 18) {
alert("Sorry, you are too young to drive this car. Powering off ");
} else if (Number(age) > 18) {
alert("Powering on. Enjoy the ride!");
} else if (Number(age) === 18 ) {
alert("Congratulations on your first year of driving. Enjoy the ride!");
}
}
<!DOCTYPE html>
<html>
<head>
<title>Javascript</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<h1>javascript in HTML</h1>
<p>HElllllooooo</p>
<script type="text/javascript">
function carsGoBrr() {
var age = prompt("What is your age?");
if (Number(age) < 18) {
alert("Sorry, you are too young to drive this car. Powering off ");
} else if (Number(age) > 18) {
alert("Powering on. Enjoy the ride!");
} else if (Number(age) === 18 ) {
alert("Congratulations on your first year of driving. Enjoy the ride!");
}
}
</script>
</body>
</html>
您是否尝试过将条件放入window.onload函数中？
window.onload = function(){
// code goes here
};
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