Mastering JavaScript

Chapter 1
The instanceof operator
One of the problems with using reference types to store values has been the use of
the typeof operator, which returns object no matter what type of object is being
referenced. To provide a solution, you can use the instanceof operator. Let's see
some examples:
var aStringObject = new String("string");
console.log(typeof aStringObject); //"object"
console.log(aStringObject instanceof String); //true
var aString = "This is a string";
console.log(aString instanceof String); //false
The third line returns false. We will discuss why this is the case when we discuss
prototype chains.
Date objects
JavaScript does not have a date data type. Instead, you can use the Date object
and its methods to work with dates and times in your applications. A Date object
is pretty exhaustive and contains several methods to handle most date- and timerelated
use cases.
JavaScript treats dates similarly to Java. JavaScript store dates as the number of
milliseconds since January 1, 1970, 00:00:00.
You can create a Date object using the following declaration:
var dataObject = new Date([parameters]);
The parameters for the Date object constructors can be as follows:
• No parameters creates today's date and time. For example, var today = new
Date();.
• A String representing a date as Month day, year hours:minutes:seconds.
For example, var twoThousandFifteen = new Date("December 31, 2015
23:59:59");. If you omit hours, minutes, or seconds, the value will be set
to 0.
• A set of integer values for the year, month, and day. For example, var
christmas = new Date(2015, 11, 25);.
• A set of integer values for the year, month, day, hour, minute, and seconds.
For example, var christmas = new Date(2015, 11, 25, 21, 00, 0);.
[ 15 ]
www.it-ebooks.info