javascript - Understanding this jQuery .shuffle() plugin or function -

could please me understand how jquery plug-in works. don't understand how .shuffle() method works. here jsbin link http://jsbin.com/yefofulohu/2/edit

jquery(function($){     // unordered list     $('button').click(function(){         $('ul').shuffle();     });  });  (function($){      $.fn.shuffle = function() {         return this.each(function(){             var items = $(this).children().clone(true);             return (items.length) ? $(this).html($.shuffle(items)) : this;         });     }      $.shuffle = function(arr) {         for(var j, x, = arr.length; i; j = parseint(math.random() * i), x = arr[--i], arr[i] = arr[j], arr[j] = x);         return arr;     }  })(jquery); 

understanding for loop's syntax understand what's happening:

for(init (optional); condition (optional); final expression (optional))    statement (optional) 

though for loops typically used specific syntax (var = 0; < arr.length; i++), can leave out or of expressions (as author of function did) , more single operation within each expression. here more verbose version of $.shuffle function commented:

$.shuffle = function(arr) {     for(var = arr.length; > 0; i--) {       // random index       var j = parseint(math.random() * i);       // x = next element       var x = arr[ - 1 ];       // next element = random element       arr[ - 1 ] = arr[j];       // random element = next element's previous value       arr[j] = x;     }     return arr; } 

instead of long-form method, opted setup variables in init expression, check i in condition expression (since decrementing, loop stop @ 0), , perform decrement , assignments in final expression.