js Math.pow什么意思

2023-02-28 14:01:02JavaScript019

$js Math.pow什么意思,第1张$

一个Math函数，

例如：Math.pow(4,3)返回4的三次幂，

用法：Math.pow(x,y)

x必需传。底数。必须是数字。

y必需传。幂数。必须是数字。

如果结果是虚数或负数，则该方法将返回 NaN。如果由于指数过大而引起浮点溢出，则该方法将返回 Infinity

++和--这是算数运算符。

比如 x=5 ，y=++x，y=6

比如 x=5 ，y=--x，y=4

+= 是赋值运算符。

比如 x+=y，相当于x=x+y

*= 比如 x*=y，相当于x=x*y

类似的符号：还有

1、除法 (/)

除法运算符的结果是操作数的商，左操作数是被除数，右操作数是除数。

2、求余 (%)

求余运算符返回第一个操作数对第二个操作数的模，即 var1 对 var2 取模，其中 var1 和 var2 是变量。取模功能就是 var1 除以 var2 的整型余数。

3、幂 (**)

幂运算符返回第一个操作数做底数，第二个操作数做指数的乘方。即， var1var2 ，其中 var1和 var2 是其两个操作数。幂运算符是右结合的。

4、一元负号 (-)

一元负号运算符位于操作数前面，并转换操作数的符号。

扩展资料

分类

C的运算符有以下几类：

注意：条件运算符是C语言中惟一一个三目(三元)运算符

参考资料来源：百度百科：运算符

1 创建脚本块

1: <script language=”JavaScript”>

2: JavaScript code goes here

3: </script>

2 隐藏脚本代码

1: <script language=”JavaScript”>

2: <!--

3: document.write(“Hello”)

4: // -->

5: </script>

在不支持JavaScript的浏览器中将不执行相关代码

3 浏览器不支持的时候显示

1: <noscript>

2: Hello to the non-JavaScript browser.

3: </noscript>

4 链接外部脚本文件

1: <script language=”JavaScript” src="http://img.sxsky.net/it//”filename.js"”></script>

5 注释脚本

1: // This is a comment

2: document.write(“Hello”)// This is a comment

3: /*

4: All of this

5: is a comment

6: */

6 输出到浏览器

1: document.write(“<strong>Hello</strong>”)

7 定义变量

1: var myVariable = “some value”

8 字符串相加

1: var myString = “String1” + “String2”

9 字符串搜索

1: <script language=”JavaScript”>

2: <!--

3: var myVariable = “Hello there”

4: var therePlace = myVariable.search(“there”)

5: document.write(therePlace)

6: // -->

7: </script>

10 字符串替换

1: thisVar.replace(“Monday”,”Friday”)

11 格式化字串

1: <script language=”JavaScript”>

2: <!--

3: var myVariable = “Hello there”

4: document.write(myVariable.big() + “<br>”)

5: document.write(myVariable.blink() + “<br>”)

6: document.write(myVariable.bold() + “<br>”)

7: document.write(myVariable.fixed() + “<br>”)

8: document.write(myVariable.fontcolor(“red”) + “<br>”)

9: document.write(myVariable.fontsize(“18pt”) + “<br>”)

10: document.write(myVariable.italics() + “<br>”)

11: document.write(myVariable.small() + “<br>”)

12: document.write(myVariable.strike() + “<br>”)

13: document.write(myVariable.sub() + “<br>”)

14: document.write(myVariable.sup() + “<br>”)

15: document.write(myVariable.toLowerCase() + “<br>”)

16: document.write(myVariable.toUpperCase() + “<br>”)

17:

18: var firstString = “My String”

19: var finalString = firstString.bold().toLowerCase().fontcolor(“red”)

20: // -->

21: </script>

12 创建数组

1: <script language=”JavaScript”>

2: <!--

3: var myArray = new Array(5)

4: myArray[0] = “First Entry”

5: myArray[1] = “Second Entry”

6: myArray[2] = “Third Entry”

7: myArray[3] = “Fourth Entry”

8: myArray[4] = “Fifth Entry”

9: var anotherArray = new Array(“First Entry”,”Second Entry”,”Third Entry”,”Fourth Entry”,”Fifth Entry”)

10: // -->

11: </script>

13 数组排序

1: <script language=”JavaScript”>

2: <!--

3: var myArray = new Array(5)

4: myArray[0] = “z”

5: myArray[1] = “c”

6: myArray[2] = “d”

7: myArray[3] = “a”

8: myArray[4] = “q”

9: document.write(myArray.sort())

10: // -->

11: </script>

14 分割字符串

1: <script language=”JavaScript”>

2: <!--

3: var myVariable = “a,b,c,d”

4: var stringArray = myVariable.split(“,”)

5: document.write(stringArray[0])

6: document.write(stringArray[1])

7: document.write(stringArray[2])

8: document.write(stringArray[3])

9: // -->

10: </script>

15 弹出警告信息

1: <script language=”JavaScript”>

2: <!--

3: window.alert(“Hello”)

4: // -->

5: </script>

16 弹出确认框

1: <script language=”JavaScript”>

2: <!--

3: var result = window.confirm(“Click OK to continue”)

4: // -->

5: </script>

17 定义函数

1: <script language=”JavaScript”>

2: <!--

3: function multiple(number1,number2) {

4: var result = number1 * number2

5: return result

6: }

7: // -->

8: </script>

18 调用JS函数

1: <a href=”#” onClick=”functionName()”>Link text</a>

2: <a href="/”javascript:functionName"()”>Link text</a>

19 在页面加载完成后执行函数

1: <body onLoad=”functionName()”>

2: Body of the page

3: </body>

20 条件判断

1: <script>

2: <!--

3: var userChoice = window.confirm(“Choose OK or Cancel”)

4: var result = (userChoice == true) ? “OK” : “Cancel”

5: document.write(result)

6: // -->

7: </script>

21 指定次数循环

1: <script>

2: <!--

3: var myArray = new Array(3)

4: myArray[0] = “Item 0”

5: myArray[1] = “Item 1”

6: myArray[2] = “Item 2”

7: for (i = 0i <myArray.lengthi++) {

8: document.write(myArray[i] + “<br>”)

9: }

10: // -->

11: </script>

22 设定将来执行

1: <script>

2: <!--

3: function hello() {

4: window.alert(“Hello”)

5: }

6: window.setTimeout(“hello()”,5000)

7: // -->

8: </script>

23 定时执行函数

1: <script>

2: <!--

3: function hello() {

4: window.alert(“Hello”)

5: window.setTimeout(“hello()”,5000)

6: }

7: window.setTimeout(“hello()”,5000)

8: // -->

9: </script>

24 取消定时执行

1: <script>

2: <!--

3: function hello() {

4: window.alert(“Hello”)

5: }

6: var myTimeout = window.setTimeout(“hello()”,5000)

7: window.clearTimeout(myTimeout)

8: // -->

9: </script>

25 在页面卸载时候执行函数

1: <body onUnload=”functionName()”>

2: Body of the page

3: </body>

JavaScript就这么回事2：浏览器输出

26 访问document对象

1: <script language=”JavaScript”>

2: var myURL = document.URL

3: window.alert(myURL)

4: </script>

27 动态输出HTML

1: <script language=”JavaScript”>

2: document.write(“<p>Here’s some information about this document:</p>”)

3: document.write(“<ul>”)

4: document.write(“<li>Referring Document: “ + document.referrer + “</li>”)

5: document.write(“<li>Domain: “ + document.domain + “</li>”)

6: document.write(“<li>URL: “ + document.URL + “</li>”)

7: document.write(“</ul>”)

8: </script>

28 输出换行

1: document.writeln(“<strong>a</strong>”)

2: document.writeln(“b”)

29 输出日期

1: <script language=”JavaScript”>

2: var thisDate = new Date()

3: document.write(thisDate.toString())

4: </script>

30 指定日期的时区

1: <script language=”JavaScript”>

2: var myOffset = -2

3: var currentDate = new Date()

4: var userOffset = currentDate.getTimezoneOffset()/60

5: var timeZoneDifference = userOffset - myOffset

6: currentDate.setHours(currentDate.getHours() + timeZoneDifference)

7: document.write(“The time and date in Central Europe is: “ + currentDate.toLocaleString())

8: </script>

31 设置日期输出格式

1: <script language=”JavaScript”>

2: var thisDate = new Date()

3: var thisTimeString = thisDate.getHours() + “:” + thisDate.getMinutes()

4: var thisDateString = thisDate.getFullYear() + “/” + thisDate.getMonth() + “/” + thisDate.getDate()

5: document.write(thisTimeString + “ on “ + thisDateString)

6: </script>

32 读取URL参数

1: <script language=”JavaScript”>

2: var urlParts = document.URL.split(“?”)

3: var parameterParts = urlParts[1].split(“&”)

4: for (i = 0i <parameterParts.lengthi++) {

5: var pairParts = parameterParts[i].split(“=”)

6: var pairName = pairParts[0]

7: var pairValue = pairParts[1]

8: document.write(pairName + “ ：“ +pairValue )

9: }

10: </script>

你还以为HTML是无状态的么？

33 打开一个新的document对象

1: <script language=”JavaScript”>

2: function newDocument() {

3: document.open()

4: document.write(“<p>This is a New Document.</p>”)

5: document.close()

6: }

7: </script>

34 页面跳转

1: <script language=”JavaScript”>

2: window.location = “http://www.liu21st.com/”

3: </script>

35 添加网页加载进度窗口

1: <html>

2: <head>

3: <script language='javaScript'>

4: var placeHolder = window.open('holder.html','placeholder','width=200,height=200')

5: </script>

6: <title>The Main Page</title>

7: </head>

8: <body onLoad='placeHolder.close()'>

9: <p>This is the main page</p>

10: </body>

11: </html>

JavaScript就这么回事3：图像

36 读取图像属性

1: <img src="http://img.sxsky.net/it//”image1.jpg"” name=”myImage”>

2: <a href=”# ” onClick=”window.alert(document.myImage.width)”>Width</a>

37 动态加载图像

1: <script language=”JavaScript”>

2: myImage = new Image

3: myImage.src = “Tellers1.jpg”

4: </script>

38 简单的图像替换

1: <script language=”JavaScript”>

2: rollImage = new Image

3: rollImage.src = “rollImage1.jpg”

4: defaultImage = new Image

5: defaultImage.src = “image1.jpg”

6: </script>

7: <a href="/”myUrl"” onMouseOver=”document.myImage.src = rollImage.src”

8: onMouseOut=”document.myImage.src = defaultImage.src”>

9: <img src="http://img.sxsky.net/it//”image1.jpg"” name=”myImage” width=100 height=100 border=0>

39 随机显示图像

1: <script language=”JavaScript”>

2: var imageList = new Array

3: imageList[0] = “image1.jpg”

4: imageList[1] = “image2.jpg”

5: imageList[2] = “image3.jpg”

6: imageList[3] = “image4.jpg”

7: var imageChoice = Math.floor(Math.random() * imageList.length)

8: document.write(‘<img src=”’ + imageList[imageChoice] + ‘“>’)

9: </script>

40 函数实现的图像替换

1: <script language=”JavaScript”>

2: var source = 0

3: var replacement = 1

4: function createRollOver(originalImage,replacementImage) {

5: var imageArray = new Array

6: imageArray[source] = new Image

7: imageArray[source].src = originalImage

8: imageArray[replacement] = new Image

9: imageArray[replacement].src = replacementImage

10: return imageArray

11: }

12: var rollImage1 = createRollOver(“image1.jpg”,”rollImage1.jpg”)

13: </script>

14: <a href=”#” onMouseOver=”document.myImage1.src = rollImage1[replacement].src”

15: onMouseOut=”document.myImage1.src = rollImage1[source].src”>

16: <img src="http://img.sxsky.net/it//”image1.jpg"” width=100 name=”myImage1” border=0>

17: </a>

41 创建幻灯片

1: <script language=”JavaScript”>

2: var imageList = new Array

3: imageList[0] = new Image

4: imageList[0].src = “image1.jpg”

5: imageList[1] = new Image

6: imageList[1].src = “image2.jpg”

7: imageList[2] = new Image

8: imageList[2].src = “image3.jpg”

9: imageList[3] = new Image

10: imageList[3].src = “image4.jpg”

11: function slideShow(imageNumber) {

12: document.slideShow.src = imageList[imageNumber].src

13: imageNumber += 1

14: if (imageNumber <imageList.length) {

15: window.setTimeout(“slideShow(“ + imageNumber + “)”,3000)

16: }

17: }

18: </script>

19: </head>

20: <body onLoad=”slideShow(0)”>

21: <img src="http://img.sxsky.net/it//”image1.jpg"” width=100 name=”slideShow”>

42 随机广告图片

1: <script language=”JavaScript”>

2: var imageList = new Array

3: imageList[0] = “image1.jpg”

4: imageList[1] = “image2.jpg”

5: imageList[2] = “image3.jpg”

6: imageList[3] = “image4.jpg”

7: var urlList = new Array

8: urlList[0] = “http://some.host/”

9: urlList[1] = “http://another.host/”

10: urlList[2] = “http://somewhere.else/”

11: urlList[3] = “http://right.here/”

12: var imageChoice = Math.floor(Math.random() * imageList.length)

13: document.write(‘<a href=”’ + urlList[imageChoice] + ‘“><img src=”’ + imageList[imageChoice] + ‘“></a>’)

14: </script>

JavaScript就这么回事4：表单

还是先继续写完JS就这么回事系列吧～

43 表单构成

1: <form method=”post” action=”target.html” name=”thisForm”>

2: <input type=”text” name=”myText”>

3: <select name=”mySelect”>

4: <option value=”1”>First Choice</option>

5: <option value=”2”>Second Choice</option>

6: </select>

7: <br>

8: <input type=”submit” value=”Submit Me”>

9: </form>

44 访问表单中的文本框内容

1: <form name=”myForm”>

2: <input type=”text” name=”myText”>

3: </form>

4: <a href='#' onClick='window.alert(document.myForm.myText.value)'>Check Text Field</a>

45 动态复制文本框内容

1: <form name=”myForm”>

2: Enter some Text: <input type=”text” name=”myText”><br>

3: Copy Text: <input type=”text” name=”copyText”>

4: </form>

5: <a href=”#” onClick=”document.myForm.copyText.value =

6: document.myForm.myText.value”>Copy Text Field</a>

46 侦测文本框的变化

1: <form name=”myForm”>

2: Enter some Text: <input type=”text” name=”myText” onChange=”alert(this.value)”>

3: </form>

47 访问选中的Select

1: <form name=”myForm”>

2: <select name=”mySelect”>

3: <option value=”First Choice”>1</option>

4: <option value=”Second Choice”>2</option>

5: <option value=”Third Choice”>3</option>

6: </select>

7: </form>

8: <a href='#' onClick='alert(document.myForm.mySelect.value)'>Check Selection List</a>

48 动态增加Select项

1: <form name=”myForm”>

2: <select name=”mySelect”>

3: <option value=”First Choice”>1</option>

4: <option value=”Second Choice”>2</option>

5: </select>

6: </form>

7: <script language=”JavaScript”>

8: document.myForm.mySelect.length++

9: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].text = “3”

10: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].value = “Third Choice”

11: </script>

49 验证表单字段

1: <script language=”JavaScript”>

2: function checkField(field) {

3: if (field.value == “”) {

4: window.alert(“You must enter a value in the field”)

5: field.focus()

6: }

7: }

8: </script>

9: <form name=”myForm” action=”target.html”>

10: Text Field: <input type=”text” name=”myField”onBlur=”checkField(this)”>

11: <br><input type=”submit”>

12: </form>

50 验证Select项

1: function checkList(selection) {

2: if (selection.length == 0) {

3: window.alert(“You must make a selection from the list.”)

4: return false

5: }

6: return true

7: }

51 动态改变表单的action

1: <form name=”myForm” action=”login.html”>

2: Username: <input type=”text” name=”username”><br>

3: Password: <input type=”password” name=”password”><br>

4: <input type=”button” value=”Login” onClick=”this.form.submit()”>

5: <input type=”button” value=”Register” onClick=”this.form.action = ‘register.html’this.form.submit()”>

6: <input type=”button” value=”Retrieve Password” onClick=”this.form.action = ‘password.html’this.form.submit()”>

7: </form>

52 使用图像按钮

1: <form name=”myForm” action=”login.html”>

2: Username: <input type=”text” name=”username”><br>

3: Password: <input type=”password”name=”password”><br>

4: <input type=”image” src="http://img.sxsky.net/it//”login.gif"” value=”Login”>

5: </form>

53 表单数据的加密

1: <SCRIPT LANGUAGE='JavaScript'>

2: <!--

3: function encrypt(item) {

4: var newItem = ''

5: for (i=0i <item.lengthi++) {

6: newItem += item.charCodeAt(i) + '.'

7: }

8: return newItem

9: }

10: function encryptForm(myForm) {

11: for (i=0i <myForm.elements.lengthi++) {

12: myForm.elements[i].value = encrypt(myForm.elements[i].value)

13: }

14: }

15:

16: //-->

17: </SCRIPT>

18: <form name='myForm' onSubmit='encryptForm(this)window.alert(this.myField.value)'>

19: Enter Some Text: <input type=text name=myField><input type=submit>

20: </form>

JavaScript就这么回事5：窗口和框架

54 改变浏览器状态栏文字提示

1: <script language=”JavaScript”>

2: window.status = “A new status message”

3: </script>

55 弹出确认提示框

1: <script language=”JavaScript”>

2: var userChoice = window.confirm(“Click OK or Cancel”)

3: if (userChoice) {

4: document.write(“You chose OK”)

5: } else {

6: document.write(“You chose Cancel”)

7: }

8: </script>

56 提示输入

1: <script language=”JavaScript”>

2: var userName = window.prompt(“Please Enter Your Name”,”Enter Your Name Here”)

3: document.write(“Your Name is “ + userName)

4: </script>

57 打开一个新窗口

1: //打开一个名称为myNewWindow的浏览器新窗口

2: <script language=”JavaScript”>

3: window.open(“http://www.liu21st.com/”,”myNewWindow”)

4: </script>

58 设置新窗口的大小

1: <script language=”JavaScript”>

2: window.open(“http://www.liu21st.com/”,”myNewWindow”,'height=300,width=300')

3: </script>

59 设置新窗口的位置

1: <script language=”JavaScript”>

2: window.open(“http://www.liu21st.com/”,”myNewWindow”,'height=300,width=300,left=200,screenX=200,top=100,screenY=100')

3: </script>

60 是否显示工具栏和滚动栏

1: <script language=”JavaScript”>

2: window.open(“http:

61 是否可以缩放新窗口的大小

1: <script language=”JavaScript”>

2: window.open('http://www.liu21st.com/' , 'myNewWindow', 'resizable=yes' )</script>

62 加载一个新的文档到当前窗口

1: <a href='#' onClick='document.location = '125a.html'' >Open New Document</a>

63 设置页面的滚动位置

1: <script language=”JavaScript”>

2: if (document.all) { //如果是IE浏览器则使用scrollTop属性

3: document.body.scrollTop = 200

4: } else { //如果是NetScape浏览器则使用pageYOffset属性

5: window.pageYOffset = 200

6: }</script>

64 在IE中打开全屏窗口

1: <a href='#' onClick=”window.open('http://www.juxta.com/','newWindow','fullScreen=yes')”>Open a full-screen window</a>

65 新窗口和父窗口的操作

1: <script language=”JavaScript”>

2: //定义新窗口

3: var newWindow = window.open(“128a.html”,”newWindow”)

4: newWindow.close()//在父窗口中关闭打开的新窗口

5: </script>

6: 在新窗口中关闭父窗口

7: window.opener.close()

66 往新窗口中写内容

1: <script language=”JavaScript”>

2: var newWindow = window.open(“”,”newWindow”)

3: newWindow.document.open()

4: newWindow.document.write(“This is a new window”)

5: newWIndow.document.close()

6: </script>

67 加载页面到框架页面

1: <frameset cols=”50%,*”>

2: <frame name=”frame1” src="http://img.sxsky.net/it//”135a.html"”>

3: <frame name=”frame2” src="http://img.sxsky.net/it//”about:blank"”>

4: </frameset>

5: 在frame1中加载frame2中的页面

6: parent.frame2.document.location = “135b.html”

68 在框架页面之间共享脚本

如果在frame1中html文件中有个脚本

1: function doAlert() {

2: window.alert(“Frame 1 is loaded”)

3: }

那么在frame2中可以如此调用该方法

1: <body onLoad=”parent.frame1.doAlert()”>

2: This is frame 2.

3: </body>

69 数据公用

可以在框架页面定义数据项，使得该数据可以被多个框架中的页面公用

1: <script language=”JavaScript”>

2: var persistentVariable = “This is a persistent value”

3: </script>

4: <frameset cols=”50%,*”>

5: <frame name=”frame1” src="http://img.sxsky.net/it//”138a.html"”>

6: <frame name=”frame2” src="http://img.sxsky.net/it//”138b.html"”>

7: </frameset>

这样在frame1和frame2中都可以使用变量persistentVariable

70 框架代码库

根据以上的一些思路，我们可以使用一个隐藏的框架页面来作为整个框架集的代码库

1: <frameset cols=”0,50%,*”>

2: <frame name=”codeFrame” src="http://img.sxsky.net/it//”140code.html"”>

3: <frame name=”frame1” src="http://img.sxsky.net/it//”140a.html"”>

4: <frame name=”frame2” src="http://img.sxsky.net/it//”140b.html"”>

5: </frameset>

词库加载错误未能找到文件“E高铁采集器内存溢出ConfigurationDictStopwordstxt”

# 上一篇：怎样查自己笔记本电脑型号的

# 下一篇：电脑显示器显示无信号是什么原因？

推荐阅读

热门文章

最新发布

标签列表

js Math.pow什么意思

给您推荐相同类型的内容：