如何在Prototype中添加JS事件处理函数？

Question

我想在Prototype中的现有事件处理程序之前添加一个事件监听器/处理程序。这里是例子：

<form ... onsubmit="alert('foo')" id="f1"> 
    $('f1').observe("submit", function() { 
    alert('do this before foo'); 
    }); 
</form> 

Answer 1

Observer = Class.create({ 
initialize: function() { 
    this.callbacks = []; 
}, 
prependCallback = function(callback) { 
    this.callbacks.unshift(callback); 
}, 
appendCallback = function(callback) { 
    this.callbacks.push(callback); 
}, 
runCallbacks = function() { 
    this.callbacks.each(
    function(callback) { 
    callback(); 
    } 
); 
} 
}); 

bunchOfCallbacks = new Observer(); 
bunchOfCallbacks.appendCallback(function(){alert('second');}); 
$('anything').observe('anyEvent', bunchOfCallbacks.runCallbacks); 
bunchOfCallbacks.prependCallback(function(){alert('first');});