JavaScript 全局事件机制

Question

我想捕获每个抛出的未定义函数错误。 JavaScript 中是否有全局错误处理工具？用例是从 flash 中捕获未定义的函数调用。

Answer 1

如何捕获未处理的 Javascript 错误

分配window.onerror事件到事件处理程序，例如:

<script type="text/javascript">
window.onerror = function(msg, url, line, col, error) {
   // Note that col & error are new to the HTML 5 spec and may not be 
   // supported in every browser.  It worked for me in Chrome.
   var extra = !col ? '' : '\ncolumn: ' + col;
   extra += !error ? '' : '\nerror: ' + error;

   // You can view the information in an alert to see things working like this:
   alert("Error: " + msg + "\nurl: " + url + "\nline: " + line + extra);

   // TODO: Report this error via ajax so you can keep track
   //       of what pages have JS issues

   var suppressErrorAlert = true;
   // If you return true, then error alerts (like in older versions of 
   // Internet Explorer) will be suppressed.
   return suppressErrorAlert;
};
</script>

如代码中所注释，如果返回值为window.onerror是 true那么浏览器应该禁止显示警告对话框。

window.onerror 事件何时触发？

简而言之，当 1.) 存在未捕获的异常或 2.) 发生编译时错误时，会引发该事件。

uncaught exceptions

• throw "some messages"
• call_something_undefined();
• cross_origin_iframe.contentWindow.document;, a security exception

compile error

• <script>{</script>
• <script>for(;)</script>
• <script>"oops</script>
• setTimeout("{", 10);, it will attempt to compile the first argument as a script

支持 window.onerror 的浏览器

• Chrome 13+
• 火狐6.0+
• Internet Explorer 5.5+
• Opera 11.60+
• Safari 5.1+

截图:

将上面的 onerror 代码添加到测试页面后的示例:

<script type="text/javascript">
call_something_undefined();
</script>

AJAX 错误报告示例

var error_data = {
    url: document.location.href,
};

if(error != null) {
    error_data['name'] = error.name; // e.g. ReferenceError
    error_data['message'] = error.line;
    error_data['stack'] = error.stack;
} else {
    error_data['msg'] = msg;
    error_data['filename'] = filename;
    error_data['line'] = line;
    error_data['col'] = col;
}

var xhr = new XMLHttpRequest();

xhr.open('POST', '/ajax/log_javascript_error');
xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
xhr.setRequestHeader('Content-Type', 'application/json');
xhr.onload = function() {
    if (xhr.status === 200) {
        console.log('JS error logged');
    } else if (xhr.status !== 200) {
        console.error('Failed to log JS error.');
        console.error(xhr);
        console.error(xhr.status);
        console.error(xhr.responseText);
    }
};
xhr.send(JSON.stringify(error_data));

JSFiddle:

https://jsfiddle.net/nzfvm44d/

引用资料:

• Mozilla Developer Network :: window.onerror
• MSDN :: Handling and Avoiding Web Page Errors Part 2: Run-Time Errors
• Back to Basics – JavaScript onerror Event
• DEV.OPERA :: Better error handling with window.onerror
• Window onError Event
• Using the onerror event to suppress JavaScript errors
• SO :: window.onerror not firing in Firefox