初学者JavaScript
[英]Beginner javascript
问题描述
I'm new to JavaScript and web design in general, and I don't understand why this doesn't work. 
我是JavaScript和Web设计的新手，但我不明白为什么这不起作用。
There are two problems. 有两个问题。
1) The title of my page doesn't work, and instead in the browser title bar what is displayed is " myHtml.html ". 1）我页面的标题不起作用，而是在浏览器标题栏中显示的是“ myHtml.html ”。 The title only works if I take the declaration of the script out. 仅当我删除script声明时，标题才有效。
2) I want the text generated by JavaScript to be blue, is there a way to do that? 2）我希望JavaScript生成的文本为蓝色，有没有办法做到这一点？
HTML: HTML：
<!DOCTYPE html>
<html>
<head class = "Header">
<title>JavaScript Test</title>
<meta charset = "UTF-8">
<link rel = "stylesheet" type = "text/css" href = "myCSS.css" >
<script type= text/javascript src= myJavaScript.js></script>
</head>
<body class = "Body" onload = "testJavaScript()">
<p>
<noscript>
Your javascript is disabled
</noscript>
</p>
</body>
</html>
JavaScript: JavaScript的：
function testJavaScript(){
var message = "You Have Javascript!!";
document.writeln(message);
}
CSS: CSS：
@charset "UTF-8";
head.Header{
font-family:sans-serif;
color:green;
}
body.Body{
font-family:sans-serif;
color:blue;
}
2 个解决方案
解决方案1
4 已采纳 2013-08-27 03:31:35
When you use document.writeln after the onload event fires (like you have it in your example), the whole DOM will be deleted and therefore there is no HTML/CSS left to give you either a title or a blue text. 当在onload事件触发后使用document.writeln时（就像您在示例中一样），整个DOM将被删除，因此没有HTML / CSS留下标题或蓝色文本。
To test what you are trying to do, do this: 要测试您要执行的操作，请执行以下操作：
...
<body class="Body">
<p>
<noscript>
Your javascript is disabled
</noscript>
<script>
testJavaScript();
</script>
</p>
...
However, I would recommend you don't use document.writeln at all (unless there is a good reason) and use DOM manipulation methods to include your text (eg innerHTML ). 但是，我建议您不要使用document.writeln （除非有充分的理由），而不要使用DOM操作方法来包含您的文本（例如innerHTML ）。 @Shylo's answer is also an approach to take. @Shylo的答案也是采取的方法。
解决方案2
0 2013-08-27 03:26:44
<!DOCTYPE html>
<html>
<head class="Header">
<title>JavaScript Test</title>
<meta charset="UTF-8">
<style type="text/css">
.Body {
font-family: sans-serif;
color: blue;
}
</style>
<script type="text/javascript">
window.onload = function() {
message = document.createElement('P');
message.className = "Body";
message.innerHTML = "You Have Javascript!!";
document.body.appendChild(message);
}
</script>
</head>
<body>
<p>
<noscript>
Your javascript is disabled
</noscript>
</p>
</body>
</html>
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