最简单的方法是将代码包装在闭包中，然后仅将全局所需的那些变量手动公开给全局范围：
(function() { // Your pre here // Expose to global window['varName'] = varName;})();为了解决Crescent Fresh的评论：为了从场景中完全删除全局变量，开发人员将需要更改问题中假设的许多内容。它看起来像这样：
Javascript：
(function() { var addEvent = function(element, type, method) { if('addEventListener' in element) { element.addEventListener(type, method, false); } else if('attachEvent' in element) { element.attachEvent('on' + type, method); // If addEventListener and attachEvent are both unavailable, // use inline events. This should never happen. } else if('on' + type in element) { // If a previous inline event exists, preserve it. This isn't // tested, it may eat your baby var oldMethod = element['on' + type], newMethod = function(e) { oldMethod(e); newMethod(e); }; } else { element['on' + type] = method; } }, uploadCount = 0, startUpload = function() { var fil = document.getElementById("FileUpload" + uploadCount); if(!fil || fil.value.length == 0) { alert("Finished!"); document.forms[0].reset(); return; } disableAllFileInputs(); fil.disabled = false; alert("Uploading file " + uploadCount); document.forms[0].submit(); }; addEvent(window, 'load', function() { var frm = document.forms[0]; frm.target = "postMe"; addEvent(frm, 'submit', function() { startUpload(); return false; }); }); var iframe = document.getElementById('postHere'); addEvent(iframe, 'load', function() { uploadCount++; if(uploadCount > 1) { startUpload(); } });})();HTML：
<iframe src="test.htm" name="postHere" id="postHere"></iframe>
您 无需 在上使用内联事件处理程序
<iframe>，它仍会在每次加载此代码时触发。
关于负载事件
这是一个测试案例，表明您不需要内联
onload事件。这取决于引用同一服务器上的文件（/emptypage.php），否则您应该可以将其粘贴到页面中并运行它。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>untitled</title></head><body> <script type="text/javascript" charset="utf-8"> (function() { var addEvent = function(element, type, method) { if('addEventListener' in element) { element.addEventListener(type, method, false); } else if('attachEvent' in element) { element.attachEvent('on' + type, method); // If addEventListener and attachEvent are both unavailable, // use inline events. This should never happen. } else if('on' + type in element) { // If a previous inline event exists, preserve it. This isn't // tested, it may eat your baby var oldMethod = element['on' + type], newMethod = function(e) { oldMethod(e); newMethod(e); }; } else { element['on' + type] = method; } }; // Work around IE 6/7 bug where form submission targets // a new window instead of the iframe. SO suggestion here: // http://stackoverflow.com/q/875650 var iframe; try { iframe = document.createElement('<iframe name="postHere">'); } catch (e) { iframe = document.createElement('iframe'); iframe.name = 'postHere'; } iframe.name = 'postHere'; iframe.id = 'postHere'; iframe.src = '/emptypage.php'; addEvent(iframe, 'load', function() { alert('iframe load'); }); document.body.appendChild(iframe); var form = document.createElement('form'); form.target = 'postHere'; form.action = '/emptypage.php'; var submit = document.createElement('input'); submit.type = 'submit'; submit.value = 'Submit'; form.appendChild(submit); document.body.appendChild(form); })(); </script></body></html>每当我在Safari，Firefox，IE 6、7和8中单击“提交”按钮时，都会触发警报。
