Javascript的HTML DOM （文档对象模型）
一、HTML DOM （文档对象模型）
采用DOM的方式来操作网页的元素,通过 HTML DOM，可访问 JavaScript HTML 文档的所有元素。
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。
JavaScript 能够改变页面中的所有 HTML 元素
JavaScript 能够改变页面中的所有 HTML 属性
JavaScript 能够改变页面中的所有 CSS 样式
JavaScript 能够对页面中的所有事件做出反应
二、查找元素
通常，通过 JavaScript，您需要操作 HTML 元素。为了做到这件事情，您必须首先找到该元素。有四种方法来做这件事：
通过 id 找到 HTML 元素
通过标签名找到 HTML 元素
通过类名找到 HTML 元素
通过name获取元素数组
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><p id="p_id">送人玫瑰1</p><p class="p_class">送人玫瑰2</p><p class="p_class">送人玫瑰3</p><input type="text" name="aaa" /><br /><input type="text" name="bbb" /><script type="text/javascript">//通过id获取元素var p_id = document.getElementById("p_id");p_id.onclick = function(){//绑定单击事件this.innerText = "手有余香1";//设置内容}//通过class获取元素数组var p_class = document.getElementsByClassName("p_class")[0];p_class.onclick = function(){this.innerText = "手有余香2";}//通过标签名获取元素数组var p_tag = document.getElementsByTagName("p")[2];p_tag.onclick = function(){this.innerText = "手有余香3";}//通过name获取元素数组var aaa = document.getElementsByName("aaa")[0];aaa.value = "请输入账号";//设置属性</script></body></html>
//单击事件<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><p>一寸光阴一寸金</p><p>一寸光阴一寸金</p><p>一寸光阴一寸金</p><script type="text/javascript">var pArr = document.getElementsByTagName("p");for (var i =0;i < pArr.length;i++) {var p = pArr[i];p.onclick = function(){this.innerText = "寸金难买寸光阴";}}</script></body></html>
三、改变HTML内容
修改 HTML 内容的最简单的方法时使用 innerHTML 属性。
如需改变 HTML 元素的内容，请使用这个语法：
document.getElementById(id).innerHTML=new HTML
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="button" value="获取第一个P标签的内容" onclick="fun01()" /><input type="button" value="获取第二个P标签的内容" onclick="fun02()" /><p>用真心待人</p><p>用真心待人</p><script type="text/javascript">var p1 = document.getElementsByTagName("p")[0];p1.onclick = function(){this.innerText = "<h1>做美丽的自己</h1>";}function fun01(){alert(p1.innerText);}var p2 = document.getElementsByTagName("p")[1];p2.onclick = function(){this.innerHTML = "<h1>做美丽的自己</h1>";}function fun02(){alert(p2.innerHTML);}</script></body></html>
四、改变HTML属性值
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="button" value="获取第一张图片的属性" onclick="fun01()" /><input type="button" value="获取第二张图片的属性" onclick="fun02()" /><img src="../img/呆萌小猪.png" width="100px" height="100px" /><img src="../img/海底世界.jpg" width="100px" height="100px" /><script type="text/javascript">var img01 = document.getElementsByTagName("img")[0];img01.onclick = function(){//设置属性this.src = "../img/呆萌小猪.png";this.width = "200";this.height = "200";}function fun01(){//获取属性console.log(img01.src);console.log(img01.width);console.log(img01.height);}var img02 = document.getElementsByTagName("img")[1];img02.onclick = function(){//设置属性img02.setAttribute("src","../img/海底世界.jpg");img02.setAttribute("width","200px");img02.setAttribute("height","200px");}function fun02(){//获取属性console.log(img02.getAttribute("src"));console.log(img02.getAttribute("width"));console.log(img02.getAttribute("height"));}</script></body></html>
五、DOM_CSS-改变HTML样式
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="button" value="隐藏图片" onclick="myHidden()" /><input type="button" value="显示图片" onclick="myShow()" /><input type="button" value="获取图片的样式" onclick="getStyle()()" /><br /><img src="../img/呆萌小猪.png" width="100px" height="100x" /><script type="text/javascript">var img = document.getElementsByTagName("img")[0];function myHidden(){img.style.visibility = "hidden";}function myShow(){img.style.visibility = "visible";}function getStyle(){alert(img.style.visibility);}</script></body></html>
六、DOM_事件
1.单击事件
点击之后，更改标题内容
this代表当前被点击的对象
经过多个改版
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><h1 onclick="this.innerText = '寸金难买寸光阴'">一寸光阴一寸金</h1></body></html>
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><h1 onclick="fun01(this)">用良心做教育</h1><script type="text/javascript">function fun01(obj){obj.innerText = "做真实的自己";}</script></body></html>
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><h1>用良心做教育</h1><script type="text/javascript">var h1 = document.getElementsByTagName("h1")[0];h1.onclick = function(){this.innerText = "做真实的自己";}</script></body></html>
2.onload事件-----页面加载
onload 一般可以来做一些网页的环境准备工作
事件会在页面或图像加载完成后立即发生。
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><script type="text/javascript">//onload事件：页面加载事件，当页面的html元素以及图片资源完全加载完毕后触发的事件window.onload = function(){var h1 = document.getElementsByTagName("h1")[0];h1.onclick = function(){this.innerText = "做真实的自己";}}</script><h1>用良心做教育</h1></body></html>
3.键盘事件
监听器：onkeydown、onkeypress、onkeyup
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="text"onkeydown="myDown()"onkeypress="myPress()"onkeyup="myUp()"/><script type="text/javascript">//键盘按下事件function myDown(){console.log("down");}//键盘持续事件function myPress(){console.log("press");}//键盘松开事件function myUp(){console.log("up");}</script></body></html>
案例，设置一个文本框，每敲一个字母，会触发将输入文本转换为大写的函数。
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="text"onkeyup="myUp(this)"/><script type="text/javascript">//需求：将输入的英文字母变为大写function myUp(obj){//获取输入框的值var v = obj.value;//替换成大写v = v.toUpperCase();//再赋值给输入框obj.value = v;}</script></body></html>
4.鼠标移动事件
onMouseOver 鼠标经过时触发
onMouseUp 按下鼠标松开鼠标时触发
onMouseOut 鼠标移出时触发
onMouseMove 鼠标移动时触
!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><img src="../img/呆萌小猪.png" width="100px" height="100px" onmousedown="myDown()"onmouseup="myUp()"onmousemove="myMove()"onmouseover="myOver()"onmouseout="myOut()"/><script type="text/javascript">//鼠标按下事件function myDown(){console.log("myDown");}//鼠标松开事件function myUp(){console.log("myUp");}//鼠标移动事件function myMove(){console.log("myMove");}//鼠标移进事件function myOver(){console.log("myOver");}//鼠标移出事件function myOut(){console.log("myOut");}</script></body></html>
案例，实现一个抓迷藏的小游戏
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title><script type="text/css">img{width: 20px;height: 20px;opacity: 0.3;}</script></head><body><img src="../img/呆萌小猪.png" onmouseover="myOver(this)" onmouseout="myOut(this)"/><img src="../img/回慕.png" onmouseover="myOver(this)" onmouseout="myOut(this)"/><img src="../img/圣诞暗夜.png" onmouseover="myOver(this)" onmouseout="myOut(this)"/><img src="../img/海底世界.jpg" onmouseover="myOver(this)" onmouseout="myOut(this)"/><script type="text/javascript">//鼠标移进事件function myOver(obj){obj.style.opacity = 1;}//鼠标移出事件function myOut(obj){obj.style.opacity = 0.3;}</script></body></html>
5.焦点事件onfocus/onblur
写一个文本框，默认显示“请输入…”，光标定位到之后，自动将里面的信息清除掉
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="text" onfocus="myFocus()" onblur="myBlur()"/><script type="text/javascript">//获取焦点事件function myFocus(){console.log("focus");}//失去焦点事件function myBlur(){console.log("blur");}</script></body></html>
案例
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="text" onfocus="myFocus(this)" onblur="myBlur(this)" value="请输入账号...." /><script type="text/javascript">function myFocus(obj){if (obj.value == "请输入账号....") {obj.value = "";}}function myBlur(obj){if (obj.value.trim) {if (obj.value.trim() == "") {obj.value = "请输入账号....";}}else{if (obj.value.replace(/(^\s+)|(\s+$) /g,"") == "") {obj.value = "请输入账号....";}}}</script></body></html>
六、DOM_节点
1.添加节点和删除节点
创建新的 HTML 元素
如需向 HTML DOM 添加新元素，您必须首先创建该元素（元素节点），然后向一个已存在的元素追加该元素。
如需删除 HTML 元素，您必须首先获得该元素的父元素：
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="button" value="添加P标签" onclick="addP()"/><input type="button" value="添加Img标签" onclick="addImg()" /><input type="button" value="克隆Img标签" onclick="cloneImg()" /><input type="button" value="删除Img标签" onclick="deleteImg()" /><div id="manager"><p>段落标签</p></div><script type="text/javascript">var manager = document.getElementById("manager");function addP(){//创建P标签 -- <p></p>var p = document.createElement("p");//创建内容var text = document.createTextNode("送人玫瑰，手有余香");//将内容添加到p标签中p.appendChild(text);//将p标签添加到div中manager.appendChild(p);}function addImg(){//创建img标签var img = document.createElement("img");//设置属性img.setAttribute("src","../img/呆萌小猪.png");img.setAttribute("width","100px");img.setAttribute("height","100px");//创建br标签var br = document.createElement("br");//将img标签添加到div中manager.appendChild(img);//将br标签添加到div中manager.appendChild(br);}function cloneImg(){//获取img对象var img = document.getElementsByTagName("img")[0];//克隆var newImg = img.cloneNode(true);//true - 深入克隆//获取br对象var br = document.getElementsByTagName("br")[0];//克隆var newBr = br.cloneNode(true);//true - 深入克隆//将img标签添加到div中manager.appendChild(newImg);//将br标签添加到div中manager.appendChild(newBr);}function deleteImg(){//获取要删除的对象var img = document.getElementsByTagName("img")[0];var br = document.getElementsByTagName("br")[0];//删除manager.removeChild(img);manager.removeChild(br);}</script></body></html>
2.扩展：删除信息
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><table border="1" width="50%"><tr><th>姓名</th><th>种族</th><th>年龄</th><th>操作</th></tr><tr><td>鸿钧</td><td>先天神族</td><td>100000</td><td><input type="button" value="删除" onclick="deleteNode(this)" /></td></tr><tr><td>血河老祖</td><td>血族</td><td>500</td><td><input type="button" value="删除" onclick="deleteNode(this)" /></td></tr><tr><td>帝俊</td><td>妖族</td><td>200</td><td><input type="button" value="删除" onclick="deleteNode(this)" /></td></tr><tr><td>轩辕</td><td>人族</td><td>100</td><td><input type="button" value="删除" onclick="deleteNode(this)" /></td></tr><tr><td>玄冥</td><td>巫族</td><td>400</td><td><input type="button" value="删除" onclick="deleteNode(this)" /></td></tr></table><script type="text/javascript">function deleteNode(obj){var tr = obj.parentNode.parentNode;var table = tr.parentNode;table.removeChild(tr);}</script></body></html>
七、DOM结合案例
1.做一个计算器
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><input type="text" id="text01" />+<input type="text" id="text02" /><input type="button" value="=" onclick="add()" /><input type="text" id="text03" /><script type="text/javascript">var text01 = document.getElementById("text01");var text02 = document.getElementById("text02");var text03 = document.getElementById("text03");function add(){//注意：输入框获取的value是string类型var result = parseFloat(text01.value) + parseFloat(text02.value);text03.value = result;}</script></body></html>
2.做级联下拉列表— 二级联动（省 市）
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title></head><body><select id="province"><option value="sc">四川</option><option value="hn">湖南</option><option value="hb">湖北</option></select>省<select id="city"><option>成都</option><option>南充</option><option>宜宾</option><option>资阳</option><option>西昌</option><option>雅安</option><option>攀枝花</option></select>市<script type="text/javascript">var province = document.getElementById("province");var city = document.getElementById("city");//改变事件province.onchange = function(){var v = this.value;if(v == "sc"){addCity(["成都","眉山","雅安","乐山","宜宾","自贡","南充","资阳"]);}else if(v == "hn"){addCity(["长沙","娄底","怀化","益阳","永州","岳阳"]);}else if(v == "hb"){addCity(["武汉","仙桃","黄冈","孝感","十堰","咸宁","宜昌","恩施"]);}}function addCity(cityArr){//清空city下拉列表中的数据city.length = 0;for(var i = 0;i<cityArr.length;i++){var cityName = cityArr[i];var option = document.createElement("option");option.innerText = cityName;city.appendChild(option);}}</script></body></html>
3.表单验证
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title><style type="text/css">span{color: red;}</style></head><body><form action="#" method="post" onsubmit="return xxx()">账号：<input type="text" name="username" id="username" /><span></span><br />密码：<input type="password" name="password" id="password" /><span></span><br />确认密码：<input type="password" name="repassword" id="repassword" /><span></span><br /><input type="submit" value="修改密码" /></form><script type="text/javascript">var username = document.getElementById("username");var password = document.getElementById("password");var repassword = document.getElementById("repassword");var span01 = document.getElementsByTagName("span")[0];var span02 = document.getElementsByTagName("span")[1];var span03 = document.getElementsByTagName("span")[2];function xxx(){span01.innerText = "";span02.innerText = "";span03.innerText = "";var bool = true;if(username.value.trim() == ""){span01.innerText = "账号不能为空";bool = false;}if(password.value.trim() == ""){span02.innerText = "密码不能为空";bool = false;}if(repassword.value.trim() == ""){span03.innerText = "确认密码不能为空";bool = false;}else if(password.value.trim() != repassword.value.trim()){span03.innerText = "密码与确认密码不一致";bool = false;}return bool;}</script></body></html>
