javascript参考 表单元素的属性和方法 二
A text input field on an HTML form. The user can enter a word, phrase, or series of numbers in a text field.
属性
defaultValue
A string indicating the default value of a Text object.
属性源 Text
描述
The initial value of defaultValue reflects the value of the VALUE attribute. Setting defaultValue programmatically overrides the initial setting.
You can set the defaultValue property at any time. The display of the related object does not update when you set the defaultValue property, only when you set the value property.
示例
The following function evaluates the defaultValue property of objects on the surfCity form and displays the values in the msgWindow window:
function defaultGetter() {
msgWindow=window.open("")
msgWindow.document.write("hidden.defaultValue is " +
document.surfCity.hiddenObj.defaultValue + "<BR>")
msgWindow.document.write("password.defaultValue is " +
document.surfCity.passwordObj.defaultValue + "<BR>")
msgWindow.document.write("text.defaultValue is " +
document.surfCity.textObj.defaultValue + "<BR>")
msgWindow.document.write("textarea.defaultValue is " +
document.surfCity.textareaObj.defaultValue + "<BR>")
msgWindow.document.close()
}
form
An object reference specifying the form containing this object.
属性源 Text
只读
描述
每个表单元素都有一个 form 属性用于指向元素的父表单。该属性在事件控制句柄中特别有用，你可能想要由其获得当前表单中其它元素。
示例
示例 1. In the following example, the form myForm contains a Text object and a button. When the user clicks the button, the value of the Text object is set to the form's name. The button's onClick event handler uses this.form to refer to the parent form, myForm.
<FORM NAME="myForm">
Form name:<INPUT TYPE="text" NAME="text1" VALUE="Beluga">
<P>
<INPUT NAME="button1" TYPE="button" VALUE="Show Form Name"
onClick="this.form.text1.value=this.form.name">
</FORM> 示例 2. The following example shows a form with several elements. When the user clicks button2, the function showElements displays an alert dialog box containing the names of each element on the form myForm.
function showElements(theForm) {
str = "Form Elements of form " + theForm.name + ": \n "
for (i = 0; i < theForm.length; i++)
str += theForm.elements[i].name + "\n"
alert(str)
}
</script>
<FORM NAME="myForm">
Form name:<INPUT TYPE="text" NAME="text1" VALUE="Beluga">
<P>
<INPUT NAME="button1" TYPE="button" VALUE="Show Form Name"
onClick="this.form.text1.value=this.form.name">
<INPUT NAME="button2" TYPE="button" VALUE="Show Form Elements"
onClick="showElements(this.form)">
</FORM> The alert dialog box displays the following text:
JavaScript Alert:
Form Elements of form myForm:
text1
button1
button2
示例 3. The following example uses an object reference, rather than the this keyword, to refer to a form. The code returns a reference to myForm, which is a form containing myTextObject.
document.myForm.myTextObject.form
name
A string specifying the name of this object.
属性源 Text
描述
The name property initially reflects the value of the NAME attribute. Changing the name property overrides this setting. The name property is not displayed on-screen; it is used to refer to the objects programmatically.
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.
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>")
}
}
type
For all Text objects, the value of the type property is "text". This property specifies the form element's type.
属性源 Text
只读
示例
The following example writes the value of the type property for every element on a form.
for (var i = 0; i < document.form1.elements.length; i++) {
document.writeln("<BR>type is " + document.form1.elements[i].type)
}
value
A string that reflects the VALUE attribute of the object.
属性源 Text
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 value property is a string that initially reflects the VALUE attribute. This string is displayed in the text field. The value of this property changes when a user or a program modifies the field.
You can set the value property at any time. The display of the Text object updates immediately when you set the value property.
示例
The following function evaluates the value property of a group of buttons and displays it in the msgWindow window:
function valueGetter() {
var msgWindow=window.open("")
msgWindow.document.write("submitButton.value is " +
document.valueTest.submitButton.value + "<BR>")
msgWindow.document.write("resetButton.value is " +
document.valueTest.resetButton.value + "<BR>")
msgWindow.document.write("myText.value is " +
document.valueTest.myText.value + "<BR>")
msgWindow.document.close()
} This example displays the following:
submitButton.value is Query Submit
resetButton.value is Reset
myText.value is Stonefish are dangerous. The previous example assumes the buttons have been defined as follows:
<INPUT TYPE="submit" NAME="submitButton">
<INPUT TYPE="reset" NAME="resetButton">
<INPUT TYPE="text" NAME="myText" VALUE="Stonefish are dangerous.">
from:asp学习网/title:javascript参考 表单元素的属性和方法 二/ time:2007-3-30 20:26:53
本文主题表单元素
