jquery each方法

稍微记下jquery each方法利用了js的call和apply进行方法调用，看下《js权威指南》中的call和apply的用法：
function.call(thisobj, args...)
24.84.1.1. Arguments
thisobj

The object on which function is to be invoked. In the body of the function, thisobj becomes the value of the this keyword. If this argument is null, the global object is used.

args...

Any number of arguments, which will be passed as arguments to function.

当我们使用$('..').each(function(){..})时，实际是进行的调用是
for(var i = i;i<$('..').length;i++){
var val = $('..')[i];
//function中的this指向val,传入的参数为$('..')的索引和索引处的值
function.call(val,i,val);
}