来看一个简易的 Javascript 调试包：jscript.debug.js，包含两个函数，第一个用来遍历对象的各个属性；第二个是一个通用的 Debug 函数（其实 说‘对象'比较‘精确些'，呵呵），用来规定各种错误级别及其各种提示、错误信息的格式化显示，还是《Javascript 实战》上面的经典例子，先看源码： 复制代码 代码如下: /** * jscript.debug package * This package contains utility functions for helping debug JavaScript. * */ /*命名空间*/ if (typeof jscript == 'undefined') { jscript = function() { } } jscript.debug = function() { } /** * This simple function is one of the handiest: pass it an object, and it * will pop an alert() listing all the properties of the object and their * values.（这个函数用来遍历对象的属性及其相应的值，并显示出来） * * @param inObj The object to display properties of. */ jscript.debug.enumProps = function(inObj) { var props = ""; var i; for (i in inObj) { props += i + " = " + inObj[i] + "n"; } alert(props); } // End enumProps(). /** * This is a very simple logger that sends all log messages to a specified * DIV.（这是一个简单的 debug 日志记录系统） */ jscript.debug.DivLogger = function() { /** * The following are faux constants that define the various levels a log * instance can be set to output.（下面的常量用来定义错误级别） */ this.LEVEL_TRACE = 1; this.LEVEL_DEBUG = 2; this.LEVEL_INFO = 3; this.LEVEL_WARN = 4; this.LEVEL_ERROR = 5; this.LEVEL_FATAL = 6; /** * These are the font colors for each logging level.（定义各种错误的显示颜色） */ this.LEVEL_TRACE_COLOR = "a0a000"; this.LEVEL_DEBUG_COLOR = "64c864"; this.LEVEL_INFO_COLOR = "000000"; this.LEVEL_WARN_COLOR = "0000ff"; this.LEVEL_ERROR_COLOR = "ff8c00"; this.LEVEL_FATAL_COLOR = "ff0000"; /** * logLevel determines the minimum message level the instance will show.（需要显示的最小错误级别，默认为 3） */ this.logLevel = 3; /** * targetDIV is the DIV object to output to. */ this.targetDiv = null; /** * This function is used to set the minimum level a log instance will show. *（在这里定义需要显示的最小错误级别） * @param inLevel One of the level constants. Any message at this level * or a higher level will be displayed, others will not. */ this.setLevel = function(inLevel) { this.logLevel = inLevel; } // End setLevel(). /** * This function is used to set the target DIV that all messages are * written to. Note that when you call this, the DIV's existing contents * are cleared out.（设置信息显示的 DIV，调用此函数的时候，原有的信息将被清除） * * @param inTargetDiv The DIV object that all messages are written to. */ this.setTargetDiv = function(inTargetDiv) { this.targetDiv = inTargetDiv; this.targetDiv.innerHTML = ""; } // End setTargetDiv(). /** * This function is called to determine if a particular message meets or * exceeds the current level of the log instance and should therefore be * logged.（此函数用来判定现有的错误级别是否应该被显示） * * @param inLevel The level of the message being checked. */ this.shouldBeLogged = function(inLevel) { if (inLevel >= this.logLevel) { return true; } else { return false; } } // End shouldBeLogged(). /** * This function logs messages at TRACE level. *（格式化显示 TRACE 的错误级别信息，往依此类推） * @param inMessage The message to log. */ this.trace = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_TRACE) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_TRACE_COLOR + ";'>" + "[TRACE] " + inMessage + "</div>"; } } // End trace(). /** * This function logs messages at DEBUG level. * * @param inMessage The message to log. */ this.debug = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_DEBUG) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_DEBUG_COLOR + ";'>" + "[DEBUG] " + inMessage + "</div>"; } } // End debug(). /** * This function logs messages at INFO level. * * @param inMessage The message to log. */ this.info = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_INFO) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_INFO_COLOR + ";'>" + "[INFO] " + inMessage + "</div>"; } } // End info(). /** * This function logs messages at WARN level. * * @param inMessage The message to log. */ this.warn = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_WARN) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_WARN_COLOR + ";'>" + "[WARN] " + inMessage + "</div>"; } } // End warn(). /** * This function logs messages at ERROR level. * * @param inMessage The message to log. */ this.error = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_ERROR) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_ERROR_COLOR + ";'>" + "[ERROR] " + inMessage + "</div>"; } } // End error(). /** * This function logs messages at FATAL level. * * @param inMessage The message to log. */ this.fatal = function(inMessage) { if (this.shouldBeLogged(this.LEVEL_FATAL) && this.targetDiv) { this.targetDiv.innerHTML += "<div style='color:#" + this.LEVEL_FATAL_COLOR + ";'>" + "[FATAL] " + inMessage + "</div>"; } } // End fatal(). } // End DivLogger(). 源码看完后，我们来测试一下这个“小包”，来看下面的测试源码： 复制代码 代码如下: <div id="jscript_debug_div" style="font-family:arial; font-size:10pt; font-weight:bold; display:none; background-color:#ffffe0; padding:4px;"> <a href="javascript:void(0);" id="enumPropsLink" onClick="jscript.debug.enumProps(document.getElementById('enumPropsLink'));"> enumProps()-Shows all the properties of this link(显示此链接标签对象的所有属性和值) </a> <br><br> <div id="divLog" style="font-family:arial; font-size: 12pt; padding: 4px; background-color:#ffffff; border:1px solid #000000; width:50%; height:300px; overflow:scroll;">Log message will appear here</div> <script> var log = new jscript.debug.DivLogger(); log.setTargetDiv(document.getElementById("divLog")); log.setLevel(log.LEVEL_DEBUG); </script> <br> <a href="javascript:void(0);" onClick="log.trace('Were tracing along now');"> DivLogger.log.trace() - Try to add a TRACE message to the above DIV (won't work because it's below the specified DEBUG level); </a><br> <a href="javascript:void(0);" onClick="log.debug('Hmm, lets do some debugging');"> DivLogger.log.debug() - Try to add a DEBUG message to the above DIV </a><br> <a href="javascript:void(0);" onClick="log.info('Just for your information');"> DivLogger.log.info() - Add a INFO message to the above DIV </a><br> <a href="javascript:void(0);" onClick="log.warn('Warning! Danger Will Robinson!');"> DivLogger.log.warn() - Add a WARN message to the above DIV </a><br> <a href="javascript:void(0);" onClick="log.error('Dave, there is an error in the AE-35 module');"> DivLogger.log.error() - Add a ERROR message to the above DIV </a><br> <a href="javascript:void(0);" onClick="log.fatal('Game over man, game over!!');"> DivLogger.log.fatal() - Add a FATAL message to the above DIV </a><br> <br><br> </div> 上面的测试代码里面的 <script> 段进行了 debug 的实例化，设置了显示信息的 DIV，而且设置了显示信息的最小级别为：LEVEL_DEBUG： var log = new jscript.debug.DivLogger(); log.setTargetDiv(document.getElementById("divLog")); log.setLevel(log.LEVEL_DEBUG); 来看看效果如何呢： enumProps()-Shows all the properties of this link(显示此链接标签对象的所有属性和值) Log message will appear here DivLogger.log.trace() - Try to add a TRACE message to the above DIV (won't work because it's below the specified DEBUG level); DivLogger.log.debug() - Try to add a DEBUG message to the above DIV DivLogger.log.info() - Add a INFO message to the above DIV DivLogger.log.warn() - Add a WARN message to the above DIV DivLogger.log.error() - Add a ERROR message to the above DIV DivLogger.log.fatal() - Add a FATAL message to the above DIV [Ctrl+A 全选 注:如需引入外部Js需刷新才能执行] 在点击“enumProps()-Shows all ……”（第一个 link ）的时候浏览器弹出的框如下图所示（Opera），详细地列出了你所点击的 a 标签对象的所有属性及值：

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