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Checkbox object example

 2007-11-27 17:53:21 来源:WEB开发网   
核心提示:ceil methodReturns the least integer greater than or equal to a number. 语法Math.ceil(number)number is any numeric expression or a property of an existing object.

ceil method

Returns the least integer greater than or equal to a number.

语法

Math.ceil(number)

number is any numeric expression or a property of an existing object.

用法

Math

例子

//Displays the value 46document.write(The ceil of 45.95 is  + Math.ceil(45.95))//Displays the value -45document.write(<P>The ceil of -45.95 is  + Math.ceil(-45.95))

See also

  • floor method

    charAt method

    Returns the character at the specified index.

    语法

    stringName.charAt(index)

    stringName is any string or a property of an existing object.
    index is any integer from 0 to stringName.length - 1, or a property of an existing object.

    用法

    string

    描述

    Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1. If the index you supply is out of range, JavaScript returns an empty string.

    例子

    The following example displays characters at different locations in the string Brave new world.
    var anyString=Brave new worlddocument.write(The character at index 0 is  + anyString.charAt(0))document.write(The character at index 1 is  + anyString.charAt(1))document.write(The character at index 2 is  + anyString.charAt(2))document.write(The character at index 3 is  + anyString.charAt(3))document.write(The character at index 4 is  + anyString.charAt(4))

    See also

  • indexOf, lastIndexOf methods

    checkbox object

    A checkbox on an htm form. A checkbox is a toggle switch that lets the user set a value on or off.

    语法

    To define a checkbox, use standard htm 语法 with the addition of the onClick event handler:

    <INPUT   TYPE=checkbox   NAME=checkboxName   VALUE=checkboxValue   [CHECKED]   [onClick=handlerText]>   textToDisplay
    NAME=checkboxName specifies the name of the checkbox object. You can access this value using the name property.
    VALUE=checkboxValue specifies a value that is returned to the server when the checkbox is selected and the form is submitted. This defaults to on. You can access this value using the value property.
    CHECKED specifies that the checkbox is displayed as checked. You can access this value using the defaultChecked property.
    textToDisplay specifies the label to display beside the checkbox.

    To use a checkbox objects properties and methods:

    1. checkboxName.propertyName2. checkboxName.methodName(parameters)3. formName.elements[index].propertyName4. formName.elements[index].methodName(parameters)
    checkboxName is the value of the NAME attribute of a checkbox object.
    formName is either the value of the NAME attribute of a form object or an element in the forms array.
    index is an integer representing a checkbox object on a form.
    propertyName is one of the properties listed below.
    methodName is one of the methods listed below.

    Property of

  • form

    描述

    A checkbox object on a form looks as follows:

    Overnight delivery

    A checkbox object is a form element and must be defined within a <FORM> tag.

    Use the checked property to specify whether the checkbox is currently checked. Use the defaultChecked property to specify whether the checkbox is checked when the form is loaded.

    Properties

  • checked lets you programatically check a checkbox
  • defaultChecked reflects the CHECKED attribute
  • name reflects the NAME attribute
  • value reflects the VALUE attribute

    Methods

  • click

    Event handlers

  • onClick

    例子

    Example 1. The following example displays a group of four checkboxes that all appear checked by default.

    <B>Specify your music preferences (check all that apply):</B><br/><INPUT TYPE=checkbox NAME=musicpref_rnb CHECKED> R&B<br/><INPUT TYPE=checkbox NAME=musicpref_jazz CHECKED> Jazz<br/><INPUT TYPE=checkbox NAME=musicpref_blues CHECKED> Blues<br/><INPUT TYPE=checkbox NAME=musicpref_newage CHECKED> New Age

    Example 2. The following example contains a form with three text boxes and one checkbox. The checkbox lets the user choose whether the text fields are converted to upper case. Each text field has an onChange event handler that converts the field value to upper case if the checkbox is checked. The checkbox has an onClick event handler that converts all fields to upper case when the user checks the checkbox.

    <htm><HEAD><TITLE>Checkbox object example</TITLE></HEAD><body><B>Last name:</B><INPUT TYPE=text NAME=lastName SIZE=20 onChange=convertField(this)><br/><B>First name:</B><INPUT TYPE=text NAME=firstName SIZE=20 onChange=convertField(this)><br/><B>City:</B><INPUT TYPE=text NAME=cityName SIZE=20 onChange=convertField(this)><p><INPUT TYPE=checkBox NAME=convertUpper onClick=if (this.checked) &#123;convertAllFields()&#125; > Convert fields to upper case</FORM></BODY></htm>

    See also

  • form and radio objects

    checked property

    A Boolean value specifying the selection state of a checkbox object or radio button.

    语法

    1. checkboxName.checked2. radioName[index].checked

    checkboxName is either the value of the NAME attribute of a checkbox object or an element in the elements array.
    radioName is the value of the NAME attribute of a radio object.
    index is an integer representing a radio button in a radio object.

    Property of

    checkbox, radio

    描述

    If a checkbox or radio button is selected, the value of its checked property is true; otherwise, it is false.

    You can set the checked property at any time. The display of the checkbox or radio button updates immediately when you set the checked property.

    例子

    The following example examines an array of radio buttons called musicType on the musicForm form to determine which button is selected. The VALUE attribute of the selected button is assigned to the checkedButton variable.

    function stateChecker() {   var checkedButton =    for (var i in document.musicForm.musicType) {      if (document.musicForm.musicType[i].checked==1) {         checkedButton=document.musicForm.musicType[i].value      }   }}

    See also

  • defaultChecked property

    clear method

    Clears the document in a window.

    语法

    document.clear()

    用法

    document

    描述

    The clear method empties the content of a window, regardless of how the content of the window has been painted.

    例子

    When the following function is called, the clear method empties the contents of the msgWindow window:

    function windowCleaner() {   msgWindow.document.clear()   msgWindow.document.close()}

    See also

  • close, open, write, writeln methods

    clearTimeout method

    Cancels a timeout that was set with the setTimeout method.

    语法

    clearTimeout(timeoutID)

    timeoutID is a timeout setting that was returned by a previous call to the setTimeout method.

    用法

    frame, window

    描述

    See the 描述 for the setTimeout method.

    例子

    See the 例子 for the setTimeout method.

    See also

  • setTimeout method

    click method

    Simulates a mouse click on the calling form element.

    语法

    1. buttonName.click()2. radioName[index].click()
    3. checkboxName.click()

    buttonName is either the value of the NAME attribute of a button, reset, or submit object or an element in the elements array.
    radioName is the value of the NAME attribute of a radio object or an element in the elements array.
    index is an integer representing a radio button in a radio object.
    checkboxName is either the value of the NAME attribute of a checkbox object or an element in the elements array.

    用法

    button, checkbox, radio, reset, submit

    描述

    The effect of the click method varies according to the calling element:

  • For button, reset, and submit, performs the same action as clicking the button.
  • For a radio, selects a radio button.
  • For a checkbox, checks the checkbox and sets its value to on.

    例子

    The following example toggles the selection status of the first radio button in the musicType radio object on the musicForm form:

    document.musicForm.musicType[0].click()

    The following example toggles the selection status of the newAge checkbox on the musicForm form:

    document.musicForm.newAge.click()

    close method (document object)

    Closes an output stream and forces data sent to layout to display.

    语法

    document.close()

    用法

    document

    描述

    The close method closes a stream opened with the document.open() method. If the stream was opened to layout, the close method forces the content of the stream to display. Font style tags, such as <BIG> and <CENTER>, automatically flush a layout stream.

    The close method also stops the meteor shower in the Netscape icon and displays Document: Done in the status bar.

    例子

    The following function calls document.close() to close a stream that was opened with document.open(). The document.close() method forces the content of the stream to display in the window.
    function windowWriter1() {   var myString = Hello, world!   msgWindow.document.open()   msgWindow.document.write(myString + <P>)   msgWindow.document.close()}

    See also

  • clear, open, write, writeln methods

    close method (window object)

    Closes the specified window.

    语法

    windowReference.close()

    windowReference is a valid way of referring to a window, as described in the window object.

    用法

    window

    描述

    The close method closes the specified window. If you call close without specifying a windowReference, JavaScript closes the current window.

    In event handlers, you must specify window.close() instead of simply using close(). Due to the scoping of static objects in JavaScript, a call to close() without specifying an object name is equivalent to document.close().

    例子

    Any of the following 例子 close the current window:

    window.close()self.close()close()

    The following example closes the messageWin window:

    messageWin.close()

    This example assumes that the window was opened in a manner similar to the following:

    messageWin=window.open()

    See also

  • open method

    confirm method

    Displays a Confirm dialog box with the specified message and OK and Cancel buttons.

    语法

    confirm(message)

    message is any string or a property of an existing object.

    用法

    window

    描述

    Use the confirm method to ask the user to make a decision that requires either an OK or a Cancel. The message argument specifies a message that prompts the user for the decision. The confirm method returns true if the user chooses OK and false if the user chooses Cancel.

    Although confirm is a 用法 the window object, you do not need to specify a windowReference when you call it. For example, windowReference.confirm() is unnecessary.

    例子

    This example uses the confirm method in the confirmCleanUp() function to confirm that the user of an application really wants to quit. If the user chooses OK, the custom cleanUp() function closes the application.

    function confirmCleanUp() {   if (confirm(Are you sure you want to quit this application?)) {      cleanUp()   }}
    You can call the confirmCleanUp() function in the onClick event handler of a forms pushbutton, as shown in the following example:
    <INPUT TYPE=button VALUE=Quit onClick=confirmCleanUp()>

    See also

  • alert, prompt methods

    cookie property

    String value of a cookie, which is a small piece of information stored by the Navigator in the cookies.txt file.

    语法

    document.cookie

    Property of

    document

    描述

    Use string methods such as substring, charAt, indexOf, and lastIndexOf to determine the value stored in the cookie. See the Netscape cookie specification for a complete specification of the cookie 语法.

    You can set the cookie property at any time.

    例子

    The following function uses the cookie property to record a reminder for users of an application. The expires= component sets an expiration date for the cookie, so it persists beyond the current browser session. The format of the date must be

    Wdy, DD-Mon-YY HH:MM:SS GMT
    where Wdy is the full name of the day of the week, DD is an integer representation of the day of the month, Mon is the month, YY is the last two digits of the year, and HH, MM, and SS are two-digit representations of hours, minutes, and seconds, respectively.

    This is the same date format as returned by Date.toGMTString, except:

    • Dashes are added between the day, month, and year
    • Year is two-digit for cookies.

    For example, a valid cookie expiration date is:
    expires=Wednesday, 09-Nov-99 23:12:40 GMT

    func
    		  
  • Tags:Checkbox object example

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