JavaScript: Chaining Cancelable Events - If you're not first, you're last

Another quick post on cancelable events in JavaScript. An example of a cancelable event is the keydown method. If I return false from a keydown method JavaScript will not allow the action of that keydown event to proceed. For example, I could return false on a document keydown event to cancel the ctrl+c behaviour etc. etc.

The following is a nice method I've built and tested only in IE 7 which allows users to chain JavaScript events together.

Obviously this could be compressed significantly.

addToObject: the HtmlElement we want to attach the cancelable event to.

eventName: the name of the event we want to trap.

methodDelegate: a JavaScript function delegate / closure for the JavaScript method to attach to the event.

order: First or Last. You can build on this however you want.

Enjoy,

function AddCancelableEvent(addToObject, eventName, methodDelegate, order) {
if (addToObject[eventName] != null) {
var oe = addToObject[eventName];
if (order == "first")
addToObject[eventName] = function(e) {
var r = methodDelegate(e);
if (r == false) return false;
return oe(e);
};
else // "if you're not first you're last" - Ricky Bobby
addToObject[eventName] = function(e) {
var r = oe(e);
if (r == false) return false;
return methodDelegate(e);
};

} else {
addToObject[eventName] = methodDelegate;
}
};


Over And Out

JavaScript: Overloading Window onload

Quick post on a very common methodology I've been using to chain events to the window.onload event in pure JavaScript:

if (window.onload == null) {
window.onload = loadAutoSubmitScript;
} else {
var ol = window.onload;
window.onload = function() { ol(); loadProc(); }
}

function loadProc() { alert("The window is loaded"); }

This should work for pretty much every page you use.

Over and Out

Google Street View Coming To Toronto

I had the privilege of witnessing the Google's street view car as it canvassed downtown Toronto yesterday.

Although I have a feeling the Google's street view car was stalking me, I will still grant Google the rights to use my image on their street view.

Here are the precise details of where I should appear in Toronto. Let's keep our fingers crossed for now!


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