js error-tolerant statement, even if js fails, it will not prompt an error (to prevent a yellow triangle symbol in the lower right corner of the browser, or the user experience is not good)
window.onerror=function(){return true;}
The following is a method to obtain js exception information and facilitate developers to find the problem:
1. try...catch...
<script type="text/javascript">
var txt=""
function message()
{
try
{
adddlert("Welcome guest!")
}
catch(err)
{
txt="There are errors on this page.\n\n"
txt+="Click "OK" to continue viewing this page,\n"
txt+="Click "Cancel" to return to the home page.\n\n"
if(!confirm(txt))
{
document.location.href="/index.html"
}
}
}
</script>
2. throw
<script type="text/javascript">
var x=prompt("Please enter a number between 0 and 10: ","")
try
{
if(x>10)
throw "Err1"
else if(x<0)
throw "Err2"
else if(isNaN(x))
throw "Err3"
}
catch (s)
{
if(er=="Err1")
alert("Error! The value is too large!")
if(er == "Err2")
alert("Error! The value is too small!")
if(er == "Err3")
alert("Error! The value is not a number!")
}
</script>
3. onerror
<script type="text/javascript">
onerror=handleErr
var txt=""
function handleErr(msg,url,l)
{
txt="There are errors on this page.\n\n"
txt+="错误：" + msg + "\n"
txt+="URL: " + url + "\n"
txt+="行：" + l + "\n\n"
txt+="Click OK to continue.\n\n"
alert(txt)
return true
}
function message()
{
adddlert("Welcome guest!")
}
</script>
Exception handling in js
In JavaScript, try...catch can be used for exception handling. For example:
try { foo.bar();} catch (e) { alert(e.name + ": " + e.message);}
At present, the system exceptions we may get mainly include the following 6 types:
- EvalError: raised when an error occurs executing code in eval()
- RangeError: raised when a numeric variable or parameter is outside of its valid range
- ReferenceError: raised when de-referencing an invalid reference
- SyntaxError: raised when a syntax error occurs while parsing code in eval()
- TypeError: raised when a variable or parameter is not a valid type
- URIError: raised when encodeURI() or decodeURI() are passed invalid parameters
上面的六种异常对象都继承自Error对象。他们都支持以下两种构造方法:
new Error();new Error("异常信息");
手工抛出异常的方法如下：
try {
throw new Error("Whoops!");}
catch (e) {
alert(e.name + ": " + e.message);}
如要判断异常信息的类型，可在catch中进行判断：
try {
foo.bar();
} catch (e) {
if (e instanceof EvalError) {
alert(e.name + ":" + e.message);
} else if (e instanceof RangeError) {
alert(e.name + ": " + e.message); }
// etc
}
Error具有下面一些主要属性：
- description: 错误描述 (仅IE可用).
- fileName: 出错的文件名 (仅Mozilla可用).
- lineNumber: 出错的行数 (仅Mozilla可用).
- message: 错误信息 (在IE下同description)
- name: 错误类型.
- number: 错误代码 (仅IE可用).
- stack: 像Java中的Stack Trace一样的错误堆栈信息 (仅Mozilla可用).
因此为了更好的了解错误信息我们可以将catch部分改为如下形式：
try {
foo.bar();
} catch(e) {
if (browserType != BROWSER_IE) {
alert("name: " + e.name + "message: " + e.message + "lineNumber: " + e.lineNumber + "fileName: " + e.fileName + "stack: " + e.stack);
} else {
alert("name: " + e.name + "errorNumber: " + (e.number & 0xFFFF) + "message: " + e.message "); } } "
JavaScript中的throw命令事实上可以抛出任何对象，并且我们可以在catch接受到此对象。例如：
try {
throw new Date(); // 抛出当前时间对象 } catch (e) { alert(e.toLocaleString()); // 使用本地格式显示当前时间
}
转自：http://www.jb51.net/article/44713.htm
Fundebug是前端JavaScript错误实时监控平台。Fundebug的JavaScript监控插件已经能够在各种主流浏览器中自动捕获错误，并且可以获取最全面的错误信息，帮助开发者更快的Debug。