JavaScript Elements and Embed Objects

JavaScript Elements and Embed Objects

In this JavaScript tutorial, you will learn about browser objects - elements and embed, properties of elements object, length, type, embed object, properties of embed object along with syntax and examples.

elements object:

The elements object is used in JavaScript to access all form elements such as fields or buttons that are present or embedded within a form. Since each element inside the form is stored as an array element within the array elements[], the user can make use of the loop concept to access any individual element within a form in JavaScript.

For example:

document.exforsys.elements[j]

The above statement is used to access the j^th form element within the form exforsys. If a user wants to get the total number of form elements within the form exforsys, it can be written by the following statement:

document.exforsys.elements.length

Properties of elements object:

• length
• type

length:

The length property of elements object returns the total number of elements within the form. The example above depicts the usage of this property.

type:

The type property of elements object is used to return the type of the form element accessed. The returned value from this property would be a string type. In other words, the type of form elements that are returned from this property can be any one of these: button, checkbox, file, hidden, image, password, radio, reset, submit, text, textarea, select-one, select-multiple

For example:

document.exforsys.elements[j].type

The above statement returns the type of the jth form element exforsys.

An example to understand all the concepts of elements objects discussed above in detail:

In the above example, function testing can be used to check if any text box in a form from the function call has been left empty. From each element on the form where the function testing is called, using for loop on the elements array accesses this. The for loop runs until the elements.length returns the total number of elements within the form. Each element in the form is checked for text box type by using the if statement:

exforsys.elements[j].type=="text"

When if returns true then the value of this text box element is checked for empty by the if statement:

exforsys.elements[j].value==""

If this also returns true then an error message is generated for entering value and loop breaks with a false value returned to the function call.

embed object:

The embed object is used in JavaScript to access all embedded object. If a user wants to access all the embedded objects contained in a document then he or she can make use of the embeds array. The embeds array gives access to all the embedded objects associated with the document.

Properties of embed object:

• SRC
• Type
• Align
• Height
• Width
• Name
• Hidden
• Palette
• Pluginspage
• ReadyState
• Units

The programmer can make use of <embed> tag to embed Plug-in documents in a web page. The concept Plug-in documents will be detailed in later sections of this tutorial.

General syntax of using embed tag is as follows:

<embed attribues>

In the above, the SRC attribute or a Type attribute is mandatory. The user can include the remainder of the attributes mentioned above when needed.

SRC:

The SRC attribute of the embed tag denotes the documents to be embedded and displayed in the plug-in. This attribute is used more often than the Type attribute.

For example, an example to understand the usage of <embed> tag with SRC attribute.

<embed SRC="exforsys.avi">

The above denotes the location of the document to be viewed by a plug-in. The details of how the above is internally processed will be explained later in the plug-ins concepts of JavaScript chapter.

Type:

The type attribute of JavaScript is used to specify the MIME type.

Height:

As the name implies, the Height attribute specifies the vertical dimension of the window area assigned to plug-in.

Width:

As the name implies, the Width attribute specifies the horizontal dimension of the window area assigned to plug-in.

Name:

Denotes the name by which the user can access the associated plug-in object.

Hidden:

This attribute helps the user to make the plug-in object visible or hidden as needed.

Palette:

This attribute denotes the mode of the plug-in color palette.

Units:

The units attribute denotes the units by which the Height and Width attributes are ascribed. The default unit is pixels.