JS点击灯泡点亮或熄灭的网页特效_html/css_WEB-ITnose
JS点击灯泡点亮或熄灭的网页特效 我们开始解释JS在HTML中作用。对于因特网和视窗操作系统，JavaScript都意味着未来。 (1)JavaScript：写入HTML输出 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <p> JavaScript 能够直接写入HTML输出流中： </p> <script type="text/javascript"> document.write("<h1 id="This-is-a-heading">This is a heading</h1>"); document.write("<p>This is a paragraph.</p>"); </script> <p> 您只能在 HTML 输出流中使用 <strong>document.write</strong>。 如果您在文档已加载后使用它（比如在函数中），会覆盖整个文档。 </p> </body> </html>提示：您只能在 HTML 输出中使用 document.write。如果您在文档加载后使用该方法，会覆盖整个文档。 (2)JavaScript：对事件作出反应 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="我的第一段-JavaScript">我的第一段 JavaScript</h1> <p> JavaScript 能够对事件作出反应。比如对按钮的点击： </p> <button type="button" onclick="alert('Welcome!')">点击这里</button> </body> </html>alert() 函数在 JavaScript 中并不常用，但它对于代码测试非常方便。onclick 事件只是您即将在本教程中学到的 众多事件之一。 (3)JavaScript：改变HTML内容 使用JavaScript来处理HTML内容是非常强大的功能。 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="我的第一段-JavaScript">我的第一段 JavaScript</h1> <p id="demo"> JavaScript能改变HTML元素的内容。 </p> <script type="text/javascript"> function myFunction() { x=document.getElementById("demo"); // 找到元素 x.innerHTML="Hello JavaScript!"; // 改变内容 } </script> <button type="button" onclick="myFunction()">点击这里</button> </body> </html>点击之后：
您会经常看到 document.getElementByID("some id")。这个方法是 HTML DOM 中定义的。DOM（文档对象模 型）是用以访问HTML元素的正式 W3C 标准。 (4)JavaScript：改变HTML图像 本例会动态地改变HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <script type="text/javascript"> function changeImage() { element=document.getElementById('myimage') if (element.src.match("bulbon")) { element.src="http://www.w3school.com.cn/i/eg_bulboff.gif"; } else { element.src="http://www.w3school.com.cn/i/eg_bulbon.gif"; } } </script> <img src="/static/imghw/default1.png" data-src="http://www.w3school.com.cn/i/eg_bulboff.gif" class="lazy" id="myimage" onclick="changeImage()" alt="JS点击灯泡点亮或熄灭的网页特效_html/css_WEB-ITnose" > <p>点击灯泡来点亮或熄灭这盏灯</p> </body> </html>点击之后：
再次点击之后：
JavaScript能够改变任意HTML元素的大多数属性，而不仅仅是图片。这是最炫酷的一个实例，也是经典的样 例！！ (5)JavaScript：改变HTML样式 改变HTML元素的样式，属于改变HTML属性的变种。 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="我的第一段-JavaScript">我的第一段 JavaScript</h1> <p id="demo"> JavaScript 能改变HTML元素的样式。 </p> <script type="text/javascript"> function myFunction() { x=document.getElementById("demo") // 找到元素 x.style.color="#ff0000"; // 改变样式 } </script> <button type="button" onclick="myFunction()">点击这里</button> </body> </html>点击按钮后：
(7)JavaScript：验证输入 JavaScript 常用于验证用户的输入。 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="我的第一段-JavaScript">我的第一段 JavaScript</h1> <p>请输入数字。如果输入值不是数字，浏览器会弹出提示框。</p> <input id="demo" type="text"> <script type="text/javascript"> function myFunction() { var x=document.getElementById("demo").value; if(x==""||isNaN(x)) { alert("Not Numeric"); } } </script> <button type="button" onclick="myFunction()">点击这里</button> </body> </html>(7)操作HTML元素 如需从JavaScript访问某个HTML元素，您可以使用 document.getElementById(id) 方法。 请使用 "id" 属性来标识 HTML 元素： 例子：通过指定的 id 来访问 HTML 元素，并改变其内容：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="My-First-Web-Page">My First Web Page</h1> <p id="demo">My First Paragraph</p> <script type="text/javascript"> document.getElementById("demo").innerHTML="My First JavaScript"; </script> </body> </html>运行的结果为：
JavaScript由web浏览器来执行。在这种情况下，浏览器将访问 id="demo" 的 HTML 元素，并把它的内容 （innerHTML）替换为 "My First JavaScript"。 (8)警告 请使用 document.write() 仅仅向文档输出写内容。 如果在文档已完成加载后执行 document.write，整个 HTML 页面将被覆盖： 实例代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JS作用</title> </head> <body> <h1 id="My-First-Web-Page">My First Web Page</h1> <p>My First Paragraph.</p> <button onclick="myFunction()">点击这里</button> <script type="text/javascript"> function myFunction() { document.write("糟糕！文档消失了。"); } </script> </body> </html>原文： http://blog.csdn.net/erlian1992/article/details/49911787
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