匹配並替換完整的JavaScript函數

Question

如何在當前頁面上匹配整個JavaScript函數？我的JavaScript函數是：

window.onbeforeunload = function() 
{ 
    if(!success) 
    { 
     success = true; 
     alert('Think first! Click CANCEL on the next page to receive a new gift.\n\n'); 
     window.location = 'http://www.mysite.com/'; 
     return '\nClick CANCEL\n\nOver thousands of gifts have been given out, get yours today!\n\n'; 
    } 
} 

，我想動態匹配和替換此功能：

window.onbeforeunload=function() 
{ 
    return ExitPopup(); 
} 

請幫我解決這個問題。

Answer 1

不能這樣做

var newFunction = function() 
{ 
    return ExitPopup(); 
} 

然後

window.onbeforeunload = newFunction;