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Getting form references

<label for=”txtComments”>Comments:</label><br />

<textarea rows=”10” cols=”50” id=”txtComments”

name=”txtComments”></textarea><br />

</form>

</body>

</html>

In this example, five form fields are described: a regular text box, a password text box, a combo box, a

multiline text box, and a Submit button. Note that with the exception of the Submit button, each field is

preceded by a

element. This element is used behind the scenes to logically tie a label to a par-

ticular form field. This feature is very useful for screen readers used by visually impaired users. The

for

attribute indicates the ID of the form field it identifies. Because of this, each form field should have

name

and

equal to the same value (

name

is submitted to the server;

identifies the element on the client).

Each type of form field can be manipulated using JavaScript. The

<form/>

element itself can also be

controlled using JavaScript to provide further control over transmission of data.

Scripting the <form/> Element

Using JavaScript with the

<form/>

element is different from using other HTML elements. You aren’t

limited to just using the core DOM methods to access forms; you can access both the

<form/>

element

itself and the form fields in a few different ways. This section covers the basic information you need to

begin scripting forms.

Getting form references

Before scripting a form, you first must get a reference to the

<form/>

element. This can be done in a

number of different ways.

First, you can use the typical method of locating an element in a DOM tree, that is, use

getElementById()

and pass in the form’s ID:

var oForm = document.getElementById(“form1”);

Alternately, you can use the

document

’s

forms

collection and reference the form either by its position in

the

forms

collection or by its

name

attribute:

var oForm = document.forms[0]; //get the first form

var oOtherForm = document.forms[“formZ”]; //get the form whose name is “formZ”

Any of these methods for retrieving a form reference is acceptable (they all return the same thing, after all).

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Forms and Data Integrity

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