There are a variety of elements (also sometimes called "controls" or "widgets") that can be used for gathering information from a form. This section looks at each control and its specific attributes. Every form control (except submit and reset) requires that you give it a name (using the name attribute) so the form-processing application can sort the information. For easier processing of form data on the server, the value of the name should not have any character spaces (use underscores or periods instead).
Input Controls: <input>
The controls described in the following sections are entered as attribute options within the <input> tag.
Text entry (type=text)
The simplest type of form element is the text entry field (type=text), which is the default setting for the <input> element. This field allows the user to enter a single word or a line of text. By default, the browser displays a text-entry box that is 20 characters wide, but you can set it to be any length using the size attribute.
By default the user can type an unlimited number of characters into the field (the display scrolls to the right if the text exceeds the width of the supplied box), but you can set a maximum number of characters using the maxlength attribute.
Use the value attribute to specify text to appear when the form is loaded. This can be changed by the user. If you have a form that consists of only one text input element, hitting the Enter key submits the form without requiring a specific Submit button in the form. The following code creates a text field with a size of 15 characters, a maximum length of 50 characters, and the text "enter your name" displayed in the field (Figure).<P>What is your name?</P><INPUT TYPE="text" NAME="name" SIZE="18" MAXLENGTH="50" VALUE="enter your name">
Figure: Text entry input
Password text entry (type=password)
A password field (type=password) works just like text entry, except the characters are obscured from view using asterisk (*) or bullet ( ) characters (which one depends on the browser). Although the characters are not displayed in the browser (Figure), the actual characters are available in the form data, so this is not a secure system for transmitting passwords. For example, the following code text reveals the actual characters in the default value:
Figure: Password input
Hidden entry (type=hidden)
The hidden input (type=hidden) adds a control that isn't displayed in the browser. It is useful for sending information to be processed along with the user-entered data, such as labels used by the script to sort forms. Some scripts require specific hidden fields be added to the form in order to function properly. Here is a hidden element (Figure):
Figure: Hidden input
Checkboxes (type=checkbox) are typically used for multiple-choice questions. They work best when more than one answer is acceptable. When the box is checked, the corresponding value is transmitted with the form to the processing program on the server.
Checkboxes can be used individually to transmit specific name/value coordinates to the server when checked. By default a checkbox is not checked; to make it checked when the page loads, simply add the checked attribute to the corresponding <input> tag.
If you assign a group of checkboxes the same name, they behave like a multiple-choice list in which the user can select more than one option for a given property, as shown in the following code and in Figure.
Figure: Multiple checkboxes in a group may be selected
Radio button (type=radio)
Radio buttons (type=radio) are used to select among choices. When a radio button is checked, its corresponding value is sent to the server for processing. Radio buttons are different from checkboxes in that when several radio buttons are grouped together by the same name, only one radio button can be selected at one time, as shown in the following code and in Figure.
Figure: Only one radio button in a group may be selected
Submit and reset buttons (type=submit; type=reset)
Every form (unless it consists of exactly one text field) needs a submit button control to initiate the transmission of information to the server. By default, the submit button (type=submit) says "Submit" or "Submit Query," but you can change it by adding your own text after the value attribute.
The reset button (type=reset) reverts all form controls back to the state they were in when the form loaded (either blank or with default values). The default value (and hence the label for the button) is "Reset," but like the submit button, you can change its text by specifying its value, as shown in Figure.<P>You have completed the form.</P><INPUT TYPE="submit"><INPUT TYPE="reset" VALUE="Start Over">
Figure: Submit and reset buttons
Some designers opt to leave the Reset button out entirely because there is no errorchecking mechanism. If a user presses it accidentally, all the data already entered is lost. This isn't an uncommon occurrence.
Custom button (type=button)
Figure: Custom button
Image button (type=image)
You can replace the submit button with a graphic of your choice by using the image input (type=image), as shown in the following code and in Figure. Clicking on the image submits the form to the server and includes the coordinates of the mouse click with the form data. You must provide the URL of the graphic with the src attribute. It is recommended that you use alternative text (with the alt attribute) for image buttons.
Figure: Using an image for a button
File selection (type=file)
The file-selection form field (type=file) lets users select a file stored on their computer and send it to the server when they submit the form. It is displayed as a text entry field with an accompanying "Browse" button for selecting the file, as shown in the following code and in Figure. Like other text fields, you can set the size and maxwidth values as well as the field's default text. When using the file input type, you should specify enctype="multipart/form-data" in the <form> tag. Ask your server administrator to confirm this setting.
Figure: The file-selection form field
Text Area: <textarea>
The <textarea> tag creates a multiline, scrollable text entry box that allows users to input extended text entries, as shown in the following code and in Figure. When the form is transmitted, the browser sends the text along with the name specified by the required name attribute.
Specify the number of lines of text the area should display using the rows attribute. The cols attribute specifies the width (measured in characters). These attributes are required according to the HTML 4.01 specification. Scrollbars are provided if the user types more text than fits in the allotted space.
Normally, the text is submitted just as it is typed in, with line returns only where the user presses the Enter key. However, you can use the wrap attribute to control text wrapping. When wrap is set to virtual or soft, the text wraps in the user's display. Physical or hard wrap settings transmit every new line with a hard-coded line return. When wrap is set to off, the default setting, the lines do not wrap. The wrap functions are browser dependent. The text that appears between <textarea> and its end tag </textarea> will be the initial contents of the text entry window when the form is displayed.<P>What did you dream last night?</P><TEXTAREA NAME="dream" ROWS="4" COLS="45">Tell us your dream in 100 words or less</TEXTAREA>
Figure: The textarea form field
Creating Menus with the <select> Tag
The <select> tag creates a menu of options that is more compact than groupings of checkboxes or radio buttons. A menu displays as either a pull-down menu or as a scrolling list of choices, depending on how the size is specified. The <select> tag works as a container for any number of <option>s.
The text between the opening and ending <option> tags is the value that is sent to the server. If you want to send a value for that choice that is not displayed in the list, use the value attribute within the <option> tag.
The <select> element displays as a pull-down menu of options when no size specification is listed (the default) or when size=1. In a pull-down menu, only one item may be selected at a time. (Note that adding the multiple attribute turns the menu into a scrolling list, as described in the next section.) By default, the first <option> in the list displays when the form loads, but you can preselect another option by adding selected within its <option> tag.
Use the selected attribute in the <option> tag to indicate the default value for the menu (the option will be highlighted when the form loads). Clicking on the arrows or bar pops up the full menu, as shown in Figure.
Figure: Items in a select menu can be set to display after menu is collapsed
To make the menu display as a scrolling list, simply specify the number of lines you'd like to be visible in the list using the size attribute, or add the multiple attribute to the <select> tag, as shown in the following code and in Figure. The multiple attribute makes it possible for users to select more than one option from the list.
Figure: Use the size attribute to display a select menu as a scrolling list
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