javascript手冊-m&n

 

Math object

A built-in object that has properties and methods for mathematical constants and functions. For example, the Math object's PI property has the value of pi.

語法

To use a Math object:

1. Math.propertyName
2. Math.methodName(parameters)

propertyName is one of the properties listed below.
methodName is one of the methods listed below.

Property of

None.

Description

The Math object is a built-in JavaScript object.

You reference the constant PI as Math.PI. Constants are defined with the full precision of real numbers in JavaScript.

Similarly, you reference Math functions as methods. For example, the sine function is Math.sin(argument), where argument is the argument.

It is often convenient to use the with statement when a section of code uses several Math constants and methods, so you don't have to type "Math" repeatedly. For example,

with (Math) {
   a = PI * r*r
   y = r*sin(theta)
   x = r*cos(theta)
}

Properties

E LN2 LN10 LOG2E LOG10E PI SQRT1_2 SQRT2

Methods

abs acos asin atan ceil cos exp floor log max min pow random round sin sqrt tan

Event handlers

None. Built-in objects do not have event handlers.

例子

See the 例子 for the individual properties and methods.

---

max method

Returns the greater of two numbers.

語法

Math.max(number1, number2)

number1 and number2 are any numeric arguments or the properties of existing objects.

Method of

Math

例子

//Displays the value 20
document.write("The maximum value is " + Math.max(10,20))

//Displays the value -10
document.write("<P>The maximum value is " + Math.max(-10,-20))

相關

min method

---

method property

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

語法

formName.method

formName is either the name of a form or an element in the forms array.

Property of

form

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".

You can set the method property at any time.

Certain values of the method property may require specific values for other form properties. See RFC 1867 for more information.

例子

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

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

相關

action, encoding, target properties

---

min method

Returns the lesser of two numbers.

語法

Math.min(number1, number2)

number1 and number2 are any numeric arguments or the properties of existing objects.

Method of

Math

例子

//Displays the value 10
document.write("

The minimum value is " + Math.min(10,20)) //Displays the value -20 document.write("<P>The minimum value is " + Math.min(-10,-20))

相關

max method

---

name property

A string specifying the name of an object.

語法

1. objectName.name
2. frameReference.name
3. frameReference.frames.name
4. radioName[index].name
5. selectName.options.name
6. windowReference.name
7. windowReference.frames.name

objectName is either the value of the NAME attribute of any of the objects listed below or an element in the elements array.
frameReference is a valid way of referring to a frame, as described in the frame object.
radioName is the value of the NAME attribute of a radio object.
selectName is either the value of the NAME attribute of a select object or an element in the elements array.
windowReference is a valid way of referring to a window, as described in the window object.

Property of

button, checkbox, frame, hidden, password, radio, reset, select, submit, text, textarea, window options array

Description

The value of the name property differs between the window object and other objects.

window object

The name property for the window object is represented by form 6 and form 7 of the 語法. The name property represents the value of the windowName argument described in the window object 語法. Both forms of the 語法 represent the same value.

name is a read-only property.

All other objects

The name property for all objects except window is represented by forms 1 through 5 of the 語法. For all objects except window, the name property initially reflects the value of the NAME attribute. Changing the name property overrides this setting.

You can set the name property at any time.

The name property is the same for every radio button in a single radio object. Individual radio buttons are referenced by their position in the radio array.

Do not confuse the name property with the label displayed on a button, reset, or submit object. The value property specifies the label for these objects. The name property is not displayed onscreen; it is used to reference the objects programatically.

For a select object, the values specified by form 1 and form 5 of the 語法 are the same. For a frame object, the values specified by forms 1, 2, and 3 of the 語法 are the same.

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.

例子

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://www.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>")
   }
}

In the following example, the first statement creates a window called netscapeWin. The second statement displays the value "netscapeHomePage" in the alert dialog box, because "netscapeHomePage" is the value of the windowName argument of netscapeWin.

netscapeWin=window.open("http://www.netscape.com", "netscapeHomePage")

alert(netscapeWin.name)

相關

For button, reset, and submit:

value property

---

navigator object

Contains information about the version of Navigator in use.

語法

To use a navigator object:

navigator.propertyName

propertyName is one of the properties listed below.

Property of

None.

Description

Use the navigator object to determine which version of the Navigator your users have.

Properties

appCodeName specifies the code name of the browser appName specifies the name of the browser appVersion specifies version information for the Navigator userAgent specifies the user-agent header

Methods

None.

Event handlers

None.

例子

See the 例子 for the individual properties.

相關

link object anchors object