JavaScript Dates

Date and Time are used in our everyday lives. It is important to understand how to use Date and Time in computer programming. You might have to create a website with a calendar. The application should show relevant times based on the user's current timezone. 

JavaScript offers us a date handling functionality through a powerful object: Date
A Date object instance represents a single point in time. Despite being named Date, it also handles time.


JavaScript Date Output

By default, JavaScript will use the browser's time zone and display a date as a full text string:

Wed Aug 08 2018 10:00:00 GMT+0200 (Central European Summer Time)

 


Learn more about JavaScript Date Formats

Create Date Objects

JS JavaScript - Create Date Objects

// creates a new date object with the current date and time
new Date()
// creates a new date object with a specified date and time, e.g. 5 numbers specify year, month, day, hour, and minute
new Date(year, month, day, hours, minutes, seconds, milliseconds)  
// If you supply only one parameter it will be treated as milliseconds since 01 January 1970
new Date(milliseconds)
// creates a new date object from a date string, e.g. "August 08, 2018 11:24:00"
new Date(date string)

Learn more about JavaScript Date Set Methods Learn more about JavaScript Date Get Methods

Comparing Dates

Comparing dates can be confusing. Take a look at the following examples to fully understand how to compare dates.


Learn more about JavaScript Comparisons

We will first show you the common misunderstanding how to compare dates.


<script>
function CompareDate() {  
   // Note: 00 is month January  
   var dateOne = new Date(2018, 00, 15); //Year, Month, Date  
   var dateTwo = new Date(2018, 00, 15); //Year, Month, Date  
 
   //NB: This code will not work when the dates are equal
   if (dateOne == dateTwo) {  
      alert("Dates are equal - NB: This will not work");  
   }
   else if (dateOne > dateTwo) {  
      alert("Date One is greater than Date Two.");  
   }
   else {  
      alert("Date Two is greater than Date One.");  
   }
}  

CompareDate();
</script>

Comparing Dates using Millisecond format

First, create a Date Object(see examples above for how to create a Date-Object).
Then, use the Date-object`s getTime() function to get the millisecond-format.
This will give you a correct result comparing dates.

JS JavaScript - Comparing Dates using Millisecond format

<script>
function CompareDate() {  
   // Note: 00 is month i.e. January  
   var dateOne = new Date(2013, 00, 15); //Year, Month, Date
   var dateTwo = new Date(2013, 00, 15); //Year, Month, Date
 
   // Using the millisecond format of the given dates
   var dateOneMillesecond = dateOne.getTime();
   var dateTwoMillesecond = dateTwo.getTime();
 
   // This code will find out when the dates are equal       
   if (dateOneMillesecond == dateTwoMillesecond) {  
      alert("Dates are equal");  
   }
   else if (dateOneMillesecond > dateTwoMillesecond) {  
      alert("Date One is greater than Date Two.");  
   }
   else  {  
      alert("Date Two is greater than Date One.");  
   }  
}

CompareDate();
</script>

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JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:

1.      HTML to define the content of web pages.

2.      CSS to specify the layout of web pages.

3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.


The benefits of using JavaScript are:

1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.


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