今天學習jQuery的核心函數.
jQuery(exPRession,[context])
這個函數接收一個包含 CSS 選擇器的字符串，然後用這個字符串去匹配一組元素。
jQuery 的核心功能都是通過這個函數實現的。 jQuery中的一切都基於這個函數，或者說都是在以某種方式使用這個函數。這個函數最基本的用法就是向它傳遞一個表達式（通常由 CSS 選擇器組成），然後根據這個表達式來查找所有匹配的元素。
默認情況下, 如果沒有指定context參數，$()將在當前的 Html 文檔中查找 DOM 元素；如果指定了 context 參數，如一個 DOM 元素集或 jQuery 對象，那就會在這個 context 中查找。(摘自jQuery API)
費話不多說直接看例子：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHtml 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html XMLns="Hello'>http://www.w3.org/1999/xhtml"><head><title>Hello World jQuery</title><style>.showtext{ background:#999999; color:#990000; font-weight:800; width:auto; height:40px;}.showtext3{ background:#666; color:#0000FF; font-weight:600; width:auto; height:30px;}</style><script type="text/javascript" src="jquery-1.3.2-vsdoc2.JS"></script></head><body><div id="divMsg" >無心測試JQuery!</div><input id="btnShow" type="button" value="顯示" /> <input id="btnHide" type="button" value="隱藏" /><br /> <input id="btnChange" type="button" value="修改內容為Hello World jQuery!" /> <input id="btnChange2" type="button" value="修改內容為 無心測試JQuery!!" /> <script type="text/Javascript">$("#btnShow").bind("click",function(event){$("#divMsg").show("fast")}); $("#btnHide").bind("click",function(event){$("#divMsg").hide("slow")}); $("#btnChange").bind("click", function(event) { $("#divMsg").html("Hello World jQuery!"); }); $("#btnChange2").bind("click",function(event){$("#divMsg").Html("無心測試JQuery!!");});</script> <h4>順便介紹下本人QQ高級群67221760(炒股群) ！</h4> <div><p>今天上班遲到啦！</p></div><div></div><div><p>不過也要按時寫博客</p></div><div><p>扣工資也無所謂啦</p></div><span>9999999999999999999</span><span class="showtext2">3333333333333333333</span><script language="Javascript">$( function() { //匹配所有的span元素， var showText=$("span"); //對所有span元素添加class屬性 showText.addClass("showtext"); //匹配所有div中含有p的元素 var selectDiv=$("div p"); //showtext的內容賦值 showText.text("93路公交車不來我有啥辦法呢"); //對selectdiv元素添加class屬性 selectDiv.addClass("showtext3"); //通過CSS類名選擇元素 var selectByClass=$(".showtext2"); selectByClass.text("我先聲明我起床很早的。"); })</script></body></Html></P>
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