1.循环序列

var arr = [12,34,56,77]
$.each(arr,function(i,j)){
    console.log(i,j)
}
$('.tbody tr').each(function(i,j){
    console.log()
})

2.循环标签

$('ul li').each(function(i,j){
    console.log(i,j)
    console.log($(this).html)
})