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JavaScript 的性能优化：加载和执行

概览无论当前JavaScript代码是内嵌还是在外链文件中，页面的下载和渲染都必须停下来等待脚本执行完成。JavaScript执行过程耗时越久，浏览器等待响应用户输入的时间就越长。浏览器在下载和执行脚本时出现阻塞的原因在于，脚本可能会改变页面或JavaScript的命名空间，它们对后面页面内容造成影响。一个典型的例子就是在页面中使用document.write()。例如清单1清单1JavaScript代码内嵌示例Sou</span> <p class="auth-span"> <span class="muted"><i class="fa fa-user"></i><span class="zj-icon-text">系统</span></span> <span class="muted"><i class="fa fa-clock-o"></i><span class="zj-icon-text">2019-08-29 22:50:45</span></span> <span class="muted"><i class="fa fa-eye"></i><span class="zj-icon-text">3543</span></span>  </p> </article><article class="excerpt"> <header> <a title="各行各业" class="label label-important zj-del-target" href="/category/38">各行各业<i class="label-arrow"></i></a> <h2> <a class="zj-titles zj-del-target" href="/article/9861" title="vb操作word" target="_blank" onclick="return recordId('',)">vb操作word </a> </h2> </header> <div class="focus"> <a class="zj-del-target" href="/article/9861" target="_blank"><img style="width: 200px; height: 123px;" class="thumb" src="/Public/static/images/article/8.jpg" alt="" title=""></a> </div> <span class="note" onclick="if (jq.browser.versions.mobile) {window.location.href='/article/9861';}else{window.open('/article/9861');}" style="cursor: pointer;">vb操作word[追加500分求教]VB操作WORD问题悬赏分：200-解决时间：2007-7-2811:42说明，用VB操作WORD,以下源码第一次操作完全正常，正常打开，正常替换，正常退出。进程中并没有留下windword的进程，但第二次继续操作时就出问题，运行到ReplaceWord()就出现462错误，关闭程序重新开始又正常。请指教出错及解决原因，追加到500分'=============打开word==============FunctionOp</span> <p class="auth-span"> <span class="muted"><i class="fa fa-user"></i><span class="zj-icon-text">系统</span></span> <span class="muted"><i class="fa fa-clock-o"></i><span class="zj-icon-text">2019-08-12 09:27:07</span></span> <span class="muted"><i class="fa fa-eye"></i><span class="zj-icon-text">3543</span></span>  </p> </article><article class="excerpt"> <header> <a title="数据库相关" class="label label-important zj-del-target" href="/category/32">数据库相关<i class="label-arrow"></i></a> <h2> <a class="zj-titles zj-del-target" href="/article/6174" title="ON、WHERE、HAVING的区别" target="_blank" onclick="return recordId('',)">ON、WHERE、HAVING的区别 </a> </h2> </header> <div class="focus"> <a class="zj-del-target" href="/article/6174" target="_blank"><img style="width: 200px; height: 123px;" class="thumb" src="/Public/static/images/article/13.jpg" alt="" title=""></a> </div> <span class="note" onclick="if (jq.browser.versions.mobile) {window.location.href='/article/6174';}else{window.open('/article/6174');}" style="cursor: pointer;">ON、WHERE、HAVING都能通过限制条件筛选数据，但他们的使用及其不同。下面我们来分析三者之间的区别。1.ON和WHERE所有的查询都回产生一个中间临时报表，查询结果就是从返回临时报表中得到。ON和WHERE后面所跟限制条件的区别，主要与限制条件起作用的时机有关，ON根据限制条件对数据库记录进行过滤，然后生产临时表；而WHERE是在临时表生产之后，根据限制条件从临时表中筛选结果。因为以上原因，ON和WHERE的区别主要有下：1）返回结果：在左外（右外</span> <p class="auth-span"> <span class="muted"><i class="fa fa-user"></i><span class="zj-icon-text">系统</span></span> <span class="muted"><i class="fa fa-clock-o"></i><span class="zj-icon-text">2019-08-12 01:52:47</span></span> <span class="muted"><i class="fa fa-eye"></i><span class="zj-icon-text">3543</span></span>  </p> </article><article class="excerpt"> <header> <a title="编程技术" class="label label-important zj-del-target" href="/category/30">编程技术<i class="label-arrow"></i></a> <h2> <a class="zj-titles zj-del-target" href="/article/13860" title="AChartEngine应用之LineChart（模拟动态生命特" target="_blank" onclick="return recordId('',)">AChartEngine应用之LineChart（模拟动态生命特 </a> </h2> </header> <div class="focus"> <a class="zj-del-target" href="/article/13860" target="_blank"><img style="width: 200px; height: 123px;" class="thumb" src="/Public/static/images/article/6.jpg" alt="" title=""></a> </div> <span class="note" onclick="if (jq.browser.versions.mobile) {window.location.href='/article/13860';}else{window.open('/article/13860');}" style="cursor: pointer;">AChartEngine应用之LineChart（模拟动态生命特征值图）接着上一次写的内容，构建动态曲线图，并产生与用户交互，考虑到数据都是活动的，不可能总是用静态数据，所以我下面的demo就是模拟。项目作用：模拟生命特征值图，动态显示分钟脉搏生命特征值走向每隔1000ms产生50组数据，并填充到表格中，主要使用的到是Handler+Task，因为我是用Activity显示这个表格每次产生的数据都需要快速的填充到主线程UI中，所以我就用Handler，这里</span> <p class="auth-span"> <span class="muted"><i class="fa fa-user"></i><span class="zj-icon-text">系统</span></span> <span class="muted"><i class="fa fa-clock-o"></i><span class="zj-icon-text">2019-08-29 22:08:56</span></span> <span class="muted"><i class="fa fa-eye"></i><span class="zj-icon-text">3542</span></span>  </p> </article><article class="excerpt"> <header> <a title="数据库相关" class="label label-important zj-del-target" href="/category/32">数据库相关<i class="label-arrow"></i></a> <h2> <a class="zj-titles zj-del-target" href="/article/6635" title="export.py" target="_blank" onclick="return recordId('',)">export.py </a> </h2> </header> <div class="focus"> <a class="zj-del-target" href="/article/6635" target="_blank"><img style="width: 200px; height: 123px;" class="thumb" src="/Public/static/images/article/11.jpg" alt="" title=""></a> </div> <span class="note" onclick="if (jq.browser.versions.mobile) {window.location.href='/article/6635';}else{window.open('/article/6635');}" style="cursor: pointer;">#!/usr/bin/envpython#encoding=utf-8importredis,codecs,sys,time,datetime,doctest,rereload(sys)sys.setdefaultencoding('utf8')classUnbuffered:def__init__(self,stream):self.stream=streamdefwrite(self,data):self.stream.write(data)self.</span> <p class="auth-span"> <span class="muted"><i class="fa fa-user"></i><span class="zj-icon-text">系统</span></span> <span class="muted"><i class="fa fa-clock-o"></i><span class="zj-icon-text">2019-08-12 01:53:20</span></span> <span class="muted"><i class="fa fa-eye"></i><span class="zj-icon-text">3542</span></span>  </p> </article><div class="pagination" style="display:;"> <ul><li><a href="/search/0/1/p/1">首页</a></li> <li class="prev-page"><a href="/search/0/1/p/184">上一页</a></li> <li><a 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