为什么这个有效的代码？

Question

http://jsbin.com/idazeg/edit#javascript,html

有人能告诉我这是如何以及为什么有效？

$('#pp').click (function () {
    ppp:doSomething('2'); //<=== ppp , how is JS **eating** this ?
});

Answer 1

ppp:是一个标签声明.它在语法上等同于:

ppp:
doSomething('2');

它在这里几乎没用,大多数开发者保留它们以允许更好地控制嵌套循环:

loop1:
for (var i = 0; i < 3; i++) {      //The first for statement is labeled "loop1"
   loop2:
   for (var j = 0; j < 3; j++) {   //The second for statement is labeled "loop2"
      if (i == 1 && j == 1) {
         continue loop1;
      } else {
         console.log("i = " + i + ", j = " + j);
      }
   }
}