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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.
创建源
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语法 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.
事件句柄
描述
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.
属性概览
方法概览
示例
示例 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>
示例 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!
示例 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>
示例 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>
参看
Button, Checkbox, FileUpload, Hidden, Password, Radio, Reset, Select, Submit, Text, Textarea.
属性
action
A string specifying a destination URL for form data that is submitted
安全性
Navigator 3.0：该属性默认是带有污点的。有关数据污点的更多信息，请看“JavaScript 的安全性”。
Navigator 4.0: Submitting a form to a mailto: or news: URL requires the UniversalSendMail privilege. 要获取 Navigator 4.0 中关于安全性更多的信息，请看“JavaScript 指南”中的第七章“JavaScript 安全性”。
描述
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描述 of the URL components.
示例
The following example sets the action property of the musicForm form to the value of the variable urlName:
document.musicForm.action=urlName
参看
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.
描述
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.
示例
See the示例 for Frame.
encoding
A string specifying the MIME encoding of the form.
描述
The encoding property initially reflects the ENCTYPE attribute of the FORM tag; however, setting encoding overrides the ENCTYPE attribute.
示例
The following function returns the value of the encoding property of musicForm:
function getEncoding() {
return document.musicForm.encoding
}
参看
Form.action, Form.method, Form.target
length
The number of elements in the form.
描述
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.
描述
The method property is a reflection of the METHOD attribute of the FORM tag. The method property should evaluate to either "get" or "post".
示例
The following function returns the value of the musicForm method property:
function getMethod() {
return document.musicForm.method
}
参看
Form.action, Form.encoding, Form.target
name
A string specifying the name of the form.
安全性
Navigator 3.0：该属性默认是带有污点的。有关数据污点的更多信息，请看“JavaScript 的安全性”。
描述
The name property initially reflects the value of the NAME attribute. Changing the name property overrides this setting.
示例
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>")
}
}
target
A string specifying the name of the window that responses go to after a form has been submitted.
描述
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.
示例
The following example specifies that responses to the musicInfo form are displayed in the msgWindow window:
document.musicInfo.target="msgWindow"
参看
Form.action, Form.encoding, Form.method
方法
handleEvent
调用指定事件的控制句柄。
语法
handleEvent(event)
参数
描述
要获得关于事件句柄的更多信息，请看“关于事件的常规信息”。
reset
Simulates a mouse click on a reset button for the calling form.
语法
reset()
参数
无
描述
The reset method restores a form element's default values. A reset button does not need to be defined for the form.
示例
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>
参看
onReset, Reset
submit
Submits a form.
语法
submit()
参数
无
安全性
Navigator 3.0: 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.
Navigator 4.0: Submitting a form to a mailto: or news: URL requires the UniversalSendMail privilege. 要获取 Navigator 4.0 中关于安全性更多的信息，请看“JavaScript 指南”中的第七章“JavaScript 安全性”。
描述
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.
示例
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.
参看
Submit, onSubmit
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