1.var now = Date.parse(new Date());

//例:1467342220000

获取的时间戳是把毫秒改成000显示.

2.var now = new Date().valueOf();

//例:1467342413494

获取了当前毫秒的时间戳.

3.var now = new Date().getTime();

//例:1467342487522

获取了当前毫秒的时间戳.