Tuesday, April 21, 2020

The Legacy DOM in JavaScript



Hello guys! morning and welcome to my tutorial on JavaScript. In my last tutorial i introduced the JavaScript Document Object Models and also listed out the three types of DOM available. I also gave a brief explanation for each of them.

So in this tutorial, i will be discussing about the Legacy Document Object Model in details with an example.

This is a method that was introduced in the early versions of JavaScript language. It is well supported by all browsers, but allows access to only certain key portions of the document, such as forms, form elements, and images.

This model provides several read only properties such as title, URL, and lastModified provides the information about the document as a whole. Apart from that, there are various methods that is provided by this model which can be used to set and get document property values.

You can also read our tutorial post on: JavaScript Math Methods


Document Properties in Legacy DOM

Below is a list of the document properties which can accessed using Legacy DOM.

Sr.No.Property & Description
1
alinkColor
Deprecated − A string that specifies the color of activated links.
Ex − document.alinkColor
2
anchors[ ]
An array of Anchor objects, one for each anchor that appears in the document
Ex − document.anchors[0], document.anchors[1] and so on
3
applets[ ]
An array of Applet objects, one for each applet that appears in the document
Ex − document.applets[0], document.applets[1] and so on
4
bgColor
Deprecated − A string that specifies the background color of the document.
Ex − document.bgColor
5
cookie
A string-valued property with special behavior that allows the cookies associated with this document to be queried and set.
Ex − document.cookie
6
domain
A string that specifies the Internet domain the document is from. Used for security purpose.
Ex − document.domain
7
embeds[ ]
An array of objects that represent data embedded in the document with the <embed> tag. A synonym for plugins[ ]. Some plugins and ActiveX controls can be controlled with JavaScript code.
Ex − document.embeds[0], document.embeds[1] and so on
8
fgColor
Deprecated - A string that specifies the default text color for the document
Ex − document.fgColor
9
forms[ ]
An array of Form objects, one for each HTML form that appears in the document.
Ex − document.forms[0], document.forms[1] and so on
10
images[ ]
An array of Image objects, one for each image that is embedded in the document with the HTML <img> tag.
Ex − document.images[0], document.images[1] and so on
11
lastModified
A read-only string that specifies the date of the most recent change to the document
Ex − document.lastModified
12
linkColor
Deprecated − A string that specifies the color of unvisited links
Ex − document.linkColor
13
links[ ]
It is a document link array.
Ex − document.links[0], document.links[1] and so on
14
location
The URL of the document. Deprecated in favor of the URL property.
Ex − document.location
15
plugins[ ]
A synonym for the embeds[ ]
Ex − document.plugins[0], document.plugins[1] and so on
16
Referrer
A read-only string that contains the URL of the document, if any, from which the current document was linked.
Ex − document.referrer
17
Title
The text contents of the <title> tag.
Ex − document.title
18
URL
A read-only string that specifies the URL of the document.
Ex − document.URL
19
vlinkColor
Deprecated − A string that specifies the color of visited links.
Ex − document.vlinkColor

You can also read our tutorial post on: Learn how to work with core JavaScript Date Properties


Document Methods in Legacy DOM

Below is the list of methods supported by the Legacy DOM.

Sr.No.Property & Description
1
clear( )
Deprecated − Erases the contents of the document and returns nothing.
Ex − document.clear( )
2
close( )
Closes a document stream opened with the open( ) method and returns nothing.
Ex − document.close( )
3
open( )
Deletes existing document content and opens a stream to which new document contents may be written. Returns nothing.
Ex − document.open( )
4
write( value, ...)
Inserts the specified string or strings into the document currently being parsed or appends to document opened with open( ). Returns nothing.
Ex − document.write( value, ...)
5
writeln( value, ...)
Identical to write( ), except that it appends a newline character to the output. Returns nothing.
Ex − document.writeln( value, ...)

Example

We can locate any HTML/XHTML element that is within any HTML document using HTML Document Object Model. For instance, if a web document contains a form element then using JavaScript, we can refer to it as document.forms[ 0 ]. If your web document two form elements, the first form is referred to as document.forms[ 0 ] and then the second as document.forns[ 1 ].

Using the hierarchy and properties given above, we can access the first form element by making use of the document.forms[ 0 ].elements[ 0 ] and so on. 

Below is an example to access the document properties using Legacy DOM method.

<html>
     <head>
          <title> Document Title </title>

          <script  type = "text/javascript">
               <!--
                    function  myFunc()  {
                         var  ret =  document.title;
                         alert("Document Title :  "  +  ret ); 

                         var  ret =  document.URL;
                         alert("Document URL :  "  +  ret );

                         var  ret =  document.forms[ 0 ];
                         alert("Document First Form :  "  +  ret );

                         var  ret =  document.forms[ 0 ].elements[ 1 ];            
                         alert("Second Element :  "  +  ret );
                    }
               //-->
          </script>

     </head>
     
     <body>
          <h1  id = "title">This is main title</h1>
          <p>Click the following below to see the result</p>

          <form  name = "FirstForm">
               <input  type = "button"  value = "Click Me"  onclick = "myFunc();"   />      
               <input  type = "button"  value = "Cancel"  />     
          </form>    

          <form  name = "SecondForm">
               <input  type = "button"  value = "Don't ClickMe" />
          </form>

     </body>
</html>

Output

Below is the output of the above example.

Document Title

This is main title

Click the following below to see the result


Note - This example returns object for forms, as well as elements and we would have to access their values by using those object properties listed above which i won't discuss in this tutorial but will discuss them in future tutorials.

Alright guys! we have come to the end of this tutorial post. In my next tutorial, i will be using an example to discuss the W3C DOM in details.

Feel free to ask your questions via the comment box below and don't forget to follow us on our various social media platforms available.

Thanks for reading and bye for now.
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