Home » » javascript Date, Time

javascript Date, Time

10:30




Javascript Date

The methods getDate(), getDay(), getMonth(), and getFullYear() allow us to retrieve date values from inside a Date object. The setDate(), setMonth(), and setFullYear() methods allow us to set the date values of an existing Date object.

The getHours(), getMinutes(), getSeconds(), and getMilliseconds() methods retrieve the time values in a Date object. The setHours(), setMinutes(), setSeconds(), and setMilliseconds() methods allow us to set time values of an existing Date object.

 One thing that we didn't cover in that chapter was the idea that the time depends on your location around the world. For example, imagine you have a chat room on your website and want to organize a chat for a certain date and time. Simply stating 15:30 is not good enough if your website attracts international visitors.

The time 15:30 could be Eastern Standard Time, Pacific Standard Time, the time in the United Kingdom, or even the time in Kuala Lumpur. You could of course say 15:30 EST and let your visitors work out what that means, but even that isn't foolproof. There is an EST in Australia as well as in the U.S.


So how does this work? In the script block at the top of the page, we have just this one line: 
var localTime = new Date();
This creates a new Date object and initializes it to the current date and time based on the client computer's clock. (Note that in fact the Date object simply stores the number of milliseconds between the date and time on your computer's clock and midnight UTC time on the 1st of January 1970.)
Within the body of the page we have seven more script blocks that use the three world time methods we looked at earlier. Note that some of them are enclosed in an if statement, for example 
if (localTime.toLocaleTimeString)
{
  document.write(localTime.toLocaleTimeString())
}
This checks to see if the browser supports that method and only makes use of it if it does. Older browsers don't support all of the date/time methods so doing this prevents ugly errors.

In the following line
document.write(localTime.toUTCString());
we write the string returned by the toUTCString() method to the page. This converts the date and time stored inside the localTime Date object to the equivalent UTC date and time.
Categories: 
Related Posts:
  • Javascript Creating Arrays The best way to create a new array is with the array literal syntax ([]),but the array constructor function is available too. If you pass a singlenumber value to the constructor function, you get an array fi lled withthat ma… Read More
  • Javascript Array You can access the contents of a simple variable just by using the variable’s name.For example, alert(lastName) opens an alert box with the value stored in the variablelastName. However, because an array can hold more than o… Read More
  • JavaScript getElementById getElementById() is a method of document object, it gets the tag element with the value "id" in its ID attribute. To reference in a JS script to a HTML tag through its ID, use the following syntax:     docum… Read More
  • Javascript While Loops A while loop repeats a chunk of code as long as a particular condition is true; in otherwords, while the condition is true. The basic structure of a while loop is this: while (condition) {// javascript to repeat} The first l… Read More
  • Javascript Cookies Cookies are small strings that let you store data across page views andsessions. These are some common uses of cookies:1. Keeping track of whether the user has logged in to your site2. Remembering that a user has visited a p… Read More
  • HTML5 Constraint Validation API HTML5 introduces the ability for browsers to validate data in forms before submitting to theserver. This capability enables basic validation even when JavaScript is unavailable or fails to load.The browser itself handles per… Read More
  • JavaScript String Length The length  returns the number of characters that are in a string, using an integer.<script type="text/javascript">var testString = "11111";var length = testString.length;document.write("The string length is: " + … Read More
  • Javascript For Loops JavaScript offers another type of loop, called a for loop, that’s a little more compact(and a little more confusing). For loops are usually used for repeating a series ofsteps a certain number of times, so they often involve… Read More
  • Javascript Event Object Properties Different types of events have different properties, which you’ll learn about later in the chapter. Here are a few properties common to all standard Event objects: ■ type The type of the event, like “click,” “loa… Read More
  • Javascript forEach Looping over arrays using functions is increasingly common, especially incertain libraries. Modern browsers support the forEach() method, butyou can also build your own.function arrayForEach(array, loopFunc) {// If the brows… Read More
  • JavaScript and HTML DOM WORKING WITH THE DOM In many cases, working with the DOM is fairly straightforward, making it easy to re-create withJavaScript what normally would be created using HTML code.   Dynamic Scripts The <script> eleme… Read More
  • Javascript Object Type Objects are created by using the new operator followed by the name of the object type to create. Developerscreate their own objects by creating instances of the Object type and adding properties and/ormethods to it, as show… Read More
  • JavaScript String indexOf var p = navigator.platform;system.win = p.indexOf(“Win”) == 0;system.mac = p.indexOf(“Mac”) == 0;system.x11 = (p.indexOf(“X11”) == 0) || (p.indexOf(“Linux”) == 0); This code uses the indexOf() method to look at the beginnin… Read More
  • JavaScript Objects Each Object instance has the following properties and methods:constructor — The function that was used to create the object. In the previous example,the constructor is the Object() function. hasOwnProperty(propertyName) — In… Read More
  • Comparing strings in JavaScript <script type="text/javascript">var username = "test";if(username == "test")    document.write("Welcome"); else    document.write("Access Denied!"); document.write("<br /><br />… Read More