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演示-JQuery中伪元素和伪类选择器

HTML代码:

 1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 2 <html xmlns="http://www.w3.org/1999/xhtml"> 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 5 <title>index</title> 6 <script type="text/javascript" src="jquery-3.1.1.min.js"></script> 7 <script type="text/javascript">     8 $(function(){ 9         $("#of").focus();//使元素提前获得焦点,以便捕捉10         })11     12     $(function(){13                $(":disabled").css("color","red");14             console.log("选择被选中(:checked)的元素,其长度为:"+$(":checked").length);15             $(":focus").css("background-color","black");16             $(":required").css("font-size","20px");17             console.log("选择enabled的表单元素,其长度为:"+$(":enabled").length);18             console.log("选择不是required的元素,其长度为:"+$(":optional").length);19             console.log("选择div中的empty的元素,其长度为:"+$("div :empty").length);20             console.log("id为t的第一个子元素的value值是:"+$("#t :first-child").val());21             $("li:last-child").css("background-color","red");22             $("ul:last-child").css("color","blue");23             $("#ull :nth-child(even)").css("color","red");24             $("div :nth-of-type(2)").css("color","gray");25             $("#ull :nth-child(4)").css("background-color","yellow");26             $("#only-type :only-of-type").css("background-color","yellow");27             $("#only :only-child").css("color","green");28         }29     );30 </script>31 </head>32 <body>33 34 <div style="border:1px solid;">35     <div>36     <a id="last" value="123" href="#">haha</a>37     <a id="last" value="123" href="#">haha</a>38         <p>兴趣:</p>39         <p>兴趣:</p>40     </div>41     <div id="t">42         <input type="checkbox" checked="checked" title="aa" value="我是first-child吗?" readonly="true"/>43         <input type="text" value="运动" id="of"/>44         <input type="checkbox"/>45         <input type="text" value="睡觉" disabled="disabled" />46         <input type="checkbox"/>47         <input type="text" value="读书"  required="required"/>48         <input type="checkbox"/>电影49     </div> 50 </div>51 <ul id="ull">52     <li>I</li>53     <li>II</li>54     <li>III</li>55     <li>IV</li>56     <li>V</li>57 </ul>58 <ul>59     <li>1</li>60     <li>2</li>61     <li>3</li>62     <li>4</li>63     <li>5</li>64 </ul>65 <div id="only" style="border:1px double"><p>我是唯一元素^_^</p></div>66 <div id="only-type" style="border:1px double"><p>我是唯一的p元素^_^</p><a>not only one~</a><br /><a>not only one~</a></div>67 </body>68 </html>

 

结果:

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演示-JQuery中伪元素和伪类选择器