使用此功能，附带日期字符串验证：

如果您在在您的项目中，

Use this function, comes with date string validation:

If you include this function somewhere in your project,

// Accepts a Date object or date string that is recognized by the Date.parse() method
function getDayOfWeek(date) {
  var dayOfWeek = new Date(date).getDay();    
  return isNaN(dayOfWeek) ? null : ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'][dayOfWeek];
}

您将能够轻松地使用它：

You will be able to use it anywhere easily like this:

getDayOfWeek("2013-07-31")
> "Wednesday"

getDayOfWeek(new Date())
> // (will return today's day. See demo jsfiddle below...)

如果无效的日期字符串是使用，将返回null。

If invalid date string is used, a null will be returned.

getDayOfWeek("~invalid~");
> null

有效的日期字符串基于 Date.parse（）方法，如MDN JavaScript参考中所述。

Valid date strings are based on the Date.parse() method as described in the MDN JavaScript reference.

演示： http：// jsfiddle。 net / samliew / fo1nnsgp /

当然你也可以使用 moment.js 插件，特别是如果涉及时区。

Of course you can also use the moment.js plugin, especially if timezones are involved.