some quick Javascript/jQuery performance tips

perftips.js

// Some references here: http://bitly.com/bundles/adrienne/15


// Using native getElementByID to create a jQuery collection is faster than jQuery's ID selector!
// -------------------------------------------------------------------------------------------------------------
// prefer: 
	$(document.getElementById("testid"));  
// to:		
	$("#testid");


// Never return false from a click handler; use preventDefault instead.
// -------------------------------------------------------------------------------------------------------------
// prefer:
	$('#item').click(function(event) {  
		// stuff here  
		event.preventDefault();
		}); 
// to:
	$('#item').click(function() {  
		// stuff here  
		return false;  
		}); 


// Contextual selectors $('element','context') are faster than unqualified selectors when not selecting by ID
// -------------------------------------------------------------------------------------------------------------
// prefer:
	$('.class', '#class-container');
// to:	
	$('.class');
// and especially to:
	$('#class-container .class');


// Using $.ready is faster than $(document).ready
// -------------------------------------------------------------------------------------------------------------
// prefer:
	$.fn.ready(function() {
		// some code
		});
// to:
	$(document).ready(function() {
		// some code
		});

		
// using CSS3 :not is faster than $fn.not !
// -------------------------------------------------------------------------------------------------------------
// prefer: 
	var d = $('div:not(#header)');
// to:		
	var d = $('div').not('#header');



// Delegating to body is faster than delegating to an arbitrary parent element
// -------------------------------------------------------------------------------------------------------------
// prefer: 
	$(document.body).on("hover", "td", function() {
		$(this).toggleClass("hover");
		});
// to:
	$("table").on("hover", "td", function() {
		$(this).toggleClass("hover");
		});
        

// $.data is faster than $fn.data
// -------------------------------------------------------------------------------------------------------------
// prefer:
	$.data( $("#el") , 'keyname' );
// to:
	$("#el").data('keyname');
    

// Appending a single (concatenated) string to a cached element is faster than appending to a live collection, 
// and WAY faster than multiple appends
// -------------------------------------------------------------------------------------------------------------
// prefer:
	var $toappend = $("#toappend");
	str = str1+str2+str3;
	$toappend.append(str);
// to:
	str = str1+str2+str3;
	 $("#toappend").append(str);
// and ABSOLUTELY to:
	 $("#toappend").append(str1);
	 $("#toappend").append(str2);
	 $("#toappend").append(str3);
	 

// Detaching nodes from the DOM before appending, then reinserting them, 
// is faster than appending to attached nodes
// -------------------------------------------------------------------------------------------------------------
// prefer:
	var $table=$("#mytable");
	var $tbody=$table.children("tbody").detach();
	$tbody.append(stuff);
	$table.append($tbody);
// to:
	var $table=$("#mytable");
	$table.children('tbody').append(stuff);
	
	
// Using quickeach plugin is faster than $fn.each
// -------------------------------------------------------------------------------------------------------------
// prefer (using plugin from https://gist.github.com/Striker21/1352993):
	$('td').quickEach(function( i, elem ){
		elem; // DOM element
		i; // DOM element index
		this; // jQuery object
		});
// to (jQuery core $fn.each method):
	$('td').each(function( i, elem ){
		this; // DOM element ( this === elem )
		i; // DOM element index
		$(this); // jQuery object
		});