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Form

Lets users input text and make choices from Form elements such as checkboxes, radio buttons, and selection lists. You can also use a form to post data to a server.

Client-side object

Implemented in

JavaScript 1.0

JavaScript 1.1: added reset method.

JavaScript 1.2: added handleEvent method.

Created by

The HTML FORM tag. The JavaScript runtime engine creates a Form object for each FORM tag in the document. You access FORM objects through the document.forms property and through named properties of that object.

To define a form, use standard HTML syntax with the addition of JavaScript event handlers. If you supply a value for the NAME attribute, you can use that value to index into the forms array. In addition, the associated document object has a named property for each named form.

Event handlers

Description

Each form in a document is a distinct object. You can refer to a form's elements in your code by using the element's name (from the NAME attribute) or the Form.elements array. The elements array contains an entry for each element (such as a Checkbox, Radio, or Text object) in a form.

If multiple objects on the same form have the same NAME attribute, an array of the given name is created automatically. Each element in the array represents an individual Form object. Elements are indexed in source order starting at 0. For example, if two Text elements and a Textarea element on the same form have their NAME attribute set to "myField", an array with the elements myField[0], myField[1], and myField[2] is created. You need to be aware of this situation in your code and know whether myField refers to a single element or to an array of elements.

Property Summary

Property Description
action

Reflects the ACTION attribute.

elements

An array reflecting all the elements in a form.

encoding

Reflects the ENCTYPE attribute.

length

Reflects the number of elements on a form.

method

Reflects the METHOD attribute.

name

Reflects the NAME attribute.

target

Reflects the TARGET attribute.

Method Summary

Method Description
handleEvent

Invokes the handler for the specified event.

reset

Simulates a mouse click on a reset button for the calling form.

submit

Submits a form.

In addition, this object inherits the watch and unwatch methods from Object.

Examples

Example 1: Named form. The following example creates a form called myForm that contains text fields for first name and last name. The form also contains two buttons that change the names to all uppercase or all lowercase. The function setCase shows how to refer to the form by its name.

<HTML>
<HEAD>
<TITLE>Form object example</TITLE>
</HEAD>
<SCRIPT>
function setCase (caseSpec){
if (caseSpec == "upper") {
   document.myForm.firstName.value=document.myForm.firstName.value.toUpperCase()
   document.myForm.lastName.value=document.myForm.lastName.value.toUpperCase()}
else {
   document.myForm.firstName.value=document.myForm.firstName.value.toLowerCase()
   document.myForm.lastName.value=document.myForm.lastName.value.toLowerCase()}
}
</SCRIPT>
<BODY>
<FORM NAME="myForm">
<B>First name:</B>
<INPUT TYPE="text" NAME="firstName" SIZE=20>
<BR><B>Last name:</B>
<INPUT TYPE="text" NAME="lastName" SIZE=20>
<P><INPUT TYPE="button" VALUE="Names to uppercase" NAME="upperButton"
   onClick="setCase('upper')">
<INPUT TYPE="button" VALUE="Names to lowercase" NAME="lowerButton"
   onClick="setCase('lower')">
</FORM>
</BODY>
</HTML>
Example 2: forms array. The onLoad event handler in the following example displays the name of the first form in an Alert dialog box.

<BODY onLoad="alert('You are looking at the ' + document.forms[0] + ' form!')">
If the form name is musicType, the alert displays the following message:

You are looking at the <object musicType> form!
Example 3: onSubmit event handler. The following example shows an onSubmit event handler that determines whether to submit a form. The form contains one Text object where the user enters three characters. onSubmit calls a function, checkData, that returns true if there are 3 characters; otherwise, it returns false. Notice that the form's onSubmit event handler, not the submit button's onClick event handler, calls the checkData function. Also, onSubmit contains a return statement that returns the value obtained with the function call.

<HTML>
<HEAD>
<TITLE>Form object/onSubmit event handler example</TITLE>
<TITLE>Form object example</TITLE>
</HEAD>
<SCRIPT>
var dataOK=false
function checkData (){
if (document.myForm.threeChar.value.length == 3) {
   return true}
   else {
      alert("Enter exactly three characters. " + document.myForm.threeChar.value +
         " is not valid.")
      return false}
}
</SCRIPT>
<BODY>
<FORM NAME="myForm" onSubmit="return checkData()">
<B>Enter 3 characters:</B>
<INPUT TYPE="text" NAME="threeChar" SIZE=3>
<P><INPUT TYPE="submit" VALUE="Done" NAME="submit1"
   onClick="document.myForm.threeChar.value=document.myForm.threeChar.value.toUpperCase()">
</FORM>
</BODY>
</HTML>
Example 4: submit method. The following example is similar to the previous one, except it submits the form using the submit method instead of a Submit object. The form's onSubmit event handler does not prevent the form from being submitted. The form uses a button's onClick event handler to call the checkData function. If the value is valid, the checkData function submits the form by calling the form's submit method.

<HTML>
<HEAD>
<TITLE>Form object/submit method example</TITLE>
</HEAD>
<SCRIPT>
var dataOK=false
function checkData (){
if (document.myForm.threeChar.value.length == 3) {
   document.myForm.submit()}
   else {
      alert("Enter exactly three characters. " + document.myForm.threeChar.value +
         " is not valid.")
      return false}
}
</SCRIPT>
<BODY>
<FORM NAME="myForm" onSubmit="alert('Form is being submitted.')">
<B>Enter 3 characters:</B>
<INPUT TYPE="text" NAME="threeChar" SIZE=3>
<P><INPUT TYPE="button" VALUE="Done" NAME="button1"
   onClick="checkData()">
</FORM>
</BODY>
</HTML>

See also

Button, Checkbox, FileUpload, Hidden, Password, Radio, Reset, Select, Submit, Text, Textarea.


action

A string specifying a destination URL for form data that is submitted

Property of

Form

Implemented in

JavaScript 1.0

Security

JavaScript 1.1: This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

JavaScript 1.2: Submitting a form to a mailto: or news: URL requires the UniversalSendMail privilege. For information on security, see the Client-Side JavaScript Guide.

Description

The action property is a reflection of the ACTION attribute of the FORM tag. Each section of a URL contains different information. See Location for a description of the URL components.

Examples

The following example sets the action property of the musicForm form to the value of the variable urlName:

document.musicForm.action=urlName

See also

Form.encoding, Form.method, Form.target


elements

An array of objects corresponding to form elements (such as checkbox, radio, and Text objects) in source order.

Property of

Form

Read-only

Implemented in

JavaScript 1.0

Description

You can refer to a form's elements in your code by using the elements array. This array contains an entry for each object (Button, Checkbox, FileUpload, Hidden, Password, Radio, Reset, Select, Submit, Text, or Textarea object) in a form in source order. Each radio button in a Radio object appears as a separate element in the elements array. For example, if a form called myForm has a text field and two checkboxes, you can refer to these elements myForm.elements[0], myForm.elements[1], and myForm.elements[2].

Although you can also refer to a form's elements by using the element's name (from the NAME attribute), the elements array provides a way to refer to Form objects programmatically without using their names. For example, if the first object on the userInfo form is the userName Text object, you can evaluate it in either of the following ways:

userInfo.userName.value
userInfo.elements[0].value
The value of each element in the elements array is the full HTML statement for the object.

Examples

See the examples for window.


encoding

A string specifying the MIME encoding of the form.

Property of

Form

Implemented in

JavaScript 1.0

Description

The encoding property initially reflects the ENCTYPE attribute of the FORM tag; however, setting encoding overrides the ENCTYPE attribute.

Examples

The following function returns the value of the encoding property of musicForm:

function getEncoding() {
   return document.musicForm.encoding
}

See also

Form.action, Form.method, Form.target


handleEvent

Invokes the handler for the specified event.

Method of

Form

Implemented in

JavaScript 1.2

Syntax

handleEvent(event)

Parameters

event

The name of an event for which the specified object has an event handler.

Description

For information on handling events, see the Client-Side JavaScript Guide.


length

The number of elements in the form.

Property of

Form

Read-only

Implemented in

JavaScript 1.0

Description

The form.length property tells you how many elements are in the form. You can get the same information using form.elements.length.


method

A string specifying how form field input information is sent to the server.

Property of

Form

Implemented in

JavaScript 1.0

Description

The method property is a reflection of the METHOD attribute of the FORM tag. The method property should evaluate to either "get" or "post".

Examples

The following function returns the value of the musicForm method property:

function getMethod() {
   return document.musicForm.method
}

See also

Form.action, Form.encoding, Form.target


name

A string specifying the name of the form.

Property of

Form

Implemented in

JavaScript 1.0

Security

JavaScript 1.1: This property is tainted by default. For information on data tainting, see the Client-Side JavaScript Guide.

Description

The name property initially reflects the value of the NAME attribute. Changing the name property overrides this setting.

Examples

In the following example, the valueGetter function uses a for loop to iterate over the array of elements on the valueTest form. The msgWindow window displays the names of all the elements on the form:

newWindow=window.open("http://home.netscape.com")
function valueGetter() {
   var msgWindow=window.open("")
   for (var i = 0; i < newWindow.document.valueTest.elements.length; i++) {
      msgWindow.document.write(newWindow.document.valueTest.elements[i].name + "<BR>")
   }
}

reset

Simulates a mouse click on a reset button for the calling form.

Method of

Form

Implemented in

JavaScript 1.1

Syntax

reset()

Parameters

None

Description

The reset method restores a form element's default values. A reset button does not need to be defined for the form.

Examples

The following example displays a Text object in which the user is to type "CA" or "AZ". The Text object's onChange event handler calls a function that executes the form's reset method if the user provides incorrect input. When the reset method executes, defaults are restored and the form's onReset event handler displays a message.

<SCRIPT>
function verifyInput(textObject) {
   if (textObject.value == 'CA' || textObject.value == 'AZ') {
      alert('Nice input')
   }
   else { document.myForm.reset() }
}
</SCRIPT>
<FORM NAME="myForm" onReset="alert('Please enter CA or AZ.')">
Enter CA or AZ:
<INPUT TYPE="text" NAME="state" SIZE="2" onChange=verifyInput(this)><P>
</FORM>

See also

onReset, Reset


submit

Submits a form.

Method of

Form

Implemented in

JavaScript 1.0

Syntax

submit()

Parameters

None

Security

JavaScript 1.1: The submit method fails without notice if the form's action is a mailto:, news:, or snews: URL. Users can submit forms with such URLs by clicking a submit button, but a confirming dialog will tell them that they are about to give away private or sensitive information.

JavaScript 1.2: Submitting a form to a mailto: or news: URL requires the UniversalSendMail privilege. For information on security, see the Client-Side JavaScript Guide.

Description

The submit method submits the specified form. It performs the same action as a submit button.

Use the submit method to send data back to an HTTP server. The submit method returns the data using either "get" or "post," as specified in Form.method.

Examples

The following example submits a form called musicChoice:

document.musicChoice.submit()
If musicChoice is the first form created, you also can submit it as follows:

document.forms[0].submit()
See also the example for Form.

See also

Submit, onSubmit


target

A string specifying the name of the window that responses go to after a form has been submitted.

Property of

Form

Implemented in

JavaScript 1.0

Description

The target property initially reflects the TARGET attribute of the A, AREA, and FORM tags; however, setting target overrides these attributes.

You can set target using a string, if the string represents a window name. The target property cannot be assigned the value of a JavaScript expression or variable.

Examples

The following example specifies that responses to the musicInfo form are displayed in the msgWindow window:

document.musicInfo.target="msgWindow"

See also

Form.action, Form.encoding, Form.method


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Last Updated: 11/16/98 12:56:23

Copyright (c) 1998 Netscape Communications Corporation