No.2 var00 = 0; document.write(var00 + ' '); var01 = 1; function foo() { document.write(var01); var01 = 1; } foo(); </ script> [Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]
No.3 </pre>输出自然就是'undefined'了。 <p> 那么函数里面是不是就屏蔽掉了全局的var01了呢？我们知道在C/C++可以使用::去访问全局变量，那么JavaScript可不可以呢？这里其实我们只要明白了全局变量到底是什么东西，就好弄了。原来全局变量都是动态添加到Window对象的实例window上的属性而以，所以我们只要在函数内用：document.write(window.var01);就可以取到其值1了。同时在这个上下文中，function内的this也是指向的window实例，我们也可以把引用写成：this.var01。 <p> By the way, 重看JScript教程时，它说变量只能是[a-zA-Z_]+[a-zA-Z0-9_]*格式，可是'$'却也可以作为变量名字符，而且还可以用在开头，比如：$1234，更甚至于：$$$ 也是合法的变量名，faint。 </p><p><script type="text/javascript" src="https://jss.51dongshi.net/pcwz/dysph.js"></script></div> <div class="downbox clearfix"> <div class="ico"><img src="https://js.51dongshi.net/tpl/pc2/images/document.png" alt="文档"></div> <div class="txt"> <h4>JScript中的'var'定义变量的作用域_javascript技巧</h4> <div class="co">JScript中的'var'定义变量的作用域_javascript技巧:都不记得是什么时候看的JScript的语法教程了，里面说在声明变量时忽略var关键字是完全合法的。当时也因为觉得JavaScript是loosely-typed的语言，所以var可能真的就是个摆设。但是事实常常又证明想当然的结果是不可靠的。 看看下面这几个例子的结果就知道问</div> <div class="tj"><b>推荐度：</b><div class="tj_stars_list"><i class="tj_stars tj_05"></i></div></div> </div> <div class="btn"> <a href="javascript:;" class="html2word" data-model="article" data-id="ahhsvd" title="文档下载"> <b>点击下载本文</b> <span>文档为doc格式</span> </a> </div> </div> <script>keji_detail_ga('article_content_bottom');</script> <div class="tvideo_tag"> 标签： <a href="/tlist-352990/">javascript</a> <a href="/tlist-7569/">变量</a> <a href="/tlist-2137257/">var</a> </div> <div class="tvideo_box tvideo_box_tab"> <div class="hd"> <ul><li class="on">热门焦点</li><script>keji_detail_ga('hot_jiaodian_tab_title');</script></ul> </div> <div class="bd"> <ul class="ult_jpic clearfix"> <script>get_hot_jiaodian_content('wz_hot_jiaodian',33,'hot',1);</script> </ul> </div> </div> </div> <!--中间文章 end--> <!--右侧专题 star--> <div class="ult_zt"> <script>keji_detail_ga('article_right_top');</script> <div class="ult_ztbox"> <h4>最新推荐</h4> <ul class="tvideo_r_a clearfix"> <script>get_detail_right('wz_right_new',33,'')</script> </ul> </div> <script>keji_detail_ga('article_right_middle');</script> <div class="ult_ztbox"> <h4>猜你喜欢</h4> <ul class="telist_rb clearfix"> <script>get_detail_right('wz_right_love',33,'')</script> </ul> </div> <script>keji_detail_ga('article_right_new_bottom');</script> <div class="ult_ztbox"> <h4>热门推荐</h4> <ul class="tvideo_r_b clearfix"> <script>get_detail_right('wz_right_hot',33,'')</script> </ul> </div> <script>keji_detail_ga('article_right_bottom');</script> </div> <!--右侧专题 end--> <div style="display:none"><a href="https://www.51dongshi.net/wzztf/ah/ahhsvd/">专题</a> </div> </div> </div> <script src="https://js.51dongshi.net/plug/qrcode/qrcode.min.js"></script> <script src="https://js.51dongshi.net/js/share.js" charset="UTF-8"></script> <script type="text/javascript" src="https://js.51dongshi.net/tpl/pc2/js/waypoints.min.js"></script> <script type="text/javascript" src="https://js.51dongshi.net/tpl/pc2/js/icon_step.js"></script> <style> #qrcode{padding: 15px;background: #fff;} </style> <div id="qrcode" style="display: none"></div> <script>new QRCode(document.getElementById("qrcode"), "https://m.51dongshi.net/eedfahhsvd.html");</script> <iframe src="https://hits.51dongshi.net/?biao=ho_article&id=955372" border="0" frameborder="0" style="width: 0px; 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