当网页被加载时，浏览器会创建页面的文档对象模型（Document Object Model）。HTML DOM 模型被构造为对象的树。
通过可编程的对象模型，JavaScript 获得了足够的能力来创建动态的 HTML。例如：改变HTML元素，改变HTML属性，改变CSS样式，事件响应。
效果图：
代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta http-equiv="Content-Language" content="zh-cn" /> <title>Javascript HTML DOM</title> <head> <style type="text/css"> body {background-color:#eeeeee} </style> </head> <body> <h3>(一)通过 id 查找 HTML 元素</h3> <p id = "hw">Hello world!</p> <script> x = document.getElementById("hw"); document.write('<p>id="hw"的段落的文本是：'+x.innerHTML+'</p>'); </script> <button onclick = "setCurrentTime()">将id="hw"的文字改为当前时间</button> <script> function setCurrentTime(){ x = document.getElementById("hw"); x.innerHTML = Date() } </script> <h3>(二)通过 标签名 查找 HTML 元素</h3> <div id = "mainDiv"> <p>This is a paragragph.</p> <p>This is another paragragph.</p> <p>Yes you're right! This is also paragragph.</p> </div> <script> xx = document.getElementById("mainDiv"); tagContents = xx.getElementsByTagName("p"); document.write("<p>使用Javascript查找id为mainDiv下的p标签的内容</p>"); for(i=0;;i++){ var tag = tagContents[i] if(tag!=null){ document.write("<p>"+tag.innerHTML+"</p>") }else{ document.write("<p>共有"+i+"条内容</p>") break; } } </script> <h3>(三)修改 HTML 的属性</h3> <img id = "bol" src = "images/eg_bulboff.gif"/> <p><button onclick = "changeSrc()">改变图片资源</button></p> <script> function changeSrc(){ x = document.getElementById("bol"); if (x.src.match("eg_bulboff.gif")){ x.src = "images/eg_bulbon.gif" }else{ x.src = "images/eg_bulboff.gif" } } </script> <h3>(四)修改 CSS 样式</h3> <p> <span id = "para_1">This is a test paragraph.</span> <button>改变文字颜色</button> </p> <p> <span id = "para_2">This is another paragraph. <button>改变字体</button> </p> <p> <span id = "para_3">This is HELLO WORLD.</span> <button>改变字号</button> </p> <p> <button>显示/隐藏</button> <span id = "para_4">示例文字</span> </p> <script> function changeTextColor(){ ele_1 = document.getElementById("para_1"); ele_1.style.color = "red"; } function changeTextFont(){ ele_2 = document.getElementById("para_2"); ele_2.style.fontFamily = "Arial"; } function changeTextSize(){ ele_3 = document.getElementById("para_3"); ele_3.style.fontSize = "larger"; } document.getElementById("para_4").style.visibility = "visible" function changeVisibility(){ ele_4 = document.getElementById("para_4"); if(ele_4.style.visibility.match("visible")){ ele_4.style.visibility = "hidden" }else{ ele_4.style.visibility = "visible" } } </script> </body> </html>
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