https://api.jquery.com/jQuery.each/
We can break the $.each() loop at a particular iteration by making the callback function return false. Returning non-false is the same as a continue statement in a for loop; it will skip immediately to the next iteration.
jQuery中each类似于javascript的for循环
但不同于for循环的是在each里面不能使用break结束循环，也不能使用continue来结束本次循环，想要实现类似的功能就只能用return,
break 用return false
continue 用return true