I personally never use $$ because when I tried it, it was noticeably slower
than other methods.
My solution to grabbing elements from a large DOM was to override
document.getElementsByClassName with a function that adds an extra parameter,
tagName. This allows it to filter elements by tagName before applying any other
filter rather than grabbing EVERY element in the DOM.
>From my unscientific tests this is considerably faster.
Example: you have a complex conglomeration of nested div, span, ul, li, a
elements that together compose a nice tree (with parent 'tree1'). You want to
get all of the drag handles at once.
Rather than
document.getElementsByClassName('handle','tree1');
I would use
document.getElementsByClassName('handle','tree1','span');
Already that cuts out probably half or more of the elements. That's half as
many regular expression matches required for a few extra characters of code,
and it is backward compatible with the original.
I have no idea why the original override in prototype doesn't do this, that
getElementsByTagName('*') just stuck out to me like a sore thumb as a prime
candidate for an easy improvement.
Of course if you want to filter by class and tag only you can
document.getElementsByClassName('handle',null,'span'); //or document.body but
that is longer to type..
----------
/* override the Prototype function, this one adds a 'tag' argument and uses
xpath where possible */
document.getElementsByClassName = function(className, parent, tagName) {
if(document.evaluate && $(parent) && $(parent).documentElement){
var xpathResult = document.evaluate("//"+(tagName||'*')+"[EMAIL
PROTECTED]'"+className+"']",
$(parent), null,
XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null);
var outArray = new Array();
for(var i=0; i<xpathResult.snapshotLength;i++){
outArray[i] = xpathResult.snapshotItem(i);}
return $A(outArray);
}else{
var children = ($(parent) ||
document).getElementsByTagName((tagName || '*'));
return $A(children).inject([], function(elements, child) {
if (child.className.match(new RegExp("(^|\\s)" +
className + "(\\s|$)")))
elements.push(Element.extend(child));
return elements;
});
}
}
Colin
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Spinoffs" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/rubyonrails-spinoffs
-~----------~----~----~----~------~----~------~--~---
