javascript网页开发第四章 JavaScript语法

第四章 JavaScript语法

4.1 JavaScript是什么

<head>

</head>

<body>

alert(new Date());

</script>

</body>

</html>

4.2 JavaScript的基本语法

4.2.1 简介

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<body>

<p>这是一个HEML段落</p>

var x=3;

alert(x);

</script>

</body>

</html>

<head>

</head>

<body>

<p>这是一个HEML段落</p>

<!--

var x=3;

alert(x);

-->

</script>

</body>

</html>

<head>

</head>

<body>

<a href="javascript:alert(new Date());">javascript</a><br />

</body>

</html>

4.2.2 JacaScript中的保留关键字

Abstract	Extends	Int	Super	Boolean
False	Interface	Switch	Break	Final
Long	Synchronized	Byte	Finally	Native
This	Case	Float	New	Throw
Catch	For	Null	Throws	Char
Function	Package	Transient	Class	Goto
Private	True	Const	If	Protected
Try	Continue	Inplements	Public	Var
Default	Import	Return	Void	Do
In	Short	While	Double	Instanceof
Static	With	Else

4.3 运算符

同Java，C，C++

<head>

</head>

<body>

for(var i=0;i<10;i++)

{

alert(i);

}

</script>

</body>

</html>

4.4 程序的流程控制

同Java，C，C++

4.5 函数

4.5.1 一般函数

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</head>

<body>

var msg="全局变量";

function square(x,y)

{

var sum;

sum=x*y+y*y;

return sum;

}

function show()

{

var msg="局部变量";

alert(msg);

}

var sum;

alert("sum="+sum);

sum=square(2,3);

alert("sum="+sum);

//上面的两句可以改写为下面的语句

//alert("sum="+square(2,3));

show();

alert(msg);

</script>

</body>

</html>

4.5.2 参数可变函数

<head>

</head>

<body>

function testparams()

{

var params="";

for(var i=0;i<arguments.length;i++)

{

params=params+" "+arguments[i];

}

alert(params);

}

testparams("abc",123);

testparams(123,456,"abc");

</script>

</body>

</html>

4.5.3 动态创建函数

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</head>

<body>

var square=new Function("x","y","var sum;sum=x*x+y*y;return sum;");

alert(square(3,2));

</script>

</body>

</html>

4.5.4 系统函数

encodeURI(string	对一个uri字符串编码后的结果
decodeURL(string)	对一个uri字符串解码后的结果
parseInt(string,编码)	把一个字符串转为整数
parseFloat(string,编码)	把一个字符串转为
isNaN	检测parseInt和parseFloat方法返回值是否为NaN

4.6 对象

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</head>

<body>

function Person()

{

}

var person1=new Person();

person1.age=18;

person1.name="王康";

alert(person1.name+":"+person1.age);

</script>

</body>

</html>

<head>

</head>

<body>

function Person()

{

}

var person1=new Person();

person1.age=18;

person1.name="王康";

//alert(person1.name+":"+person1.age);

function sayFunc()

{

alert(person1.name+":"+person1.age);

}

person1.say=sayFunc;

person1.say();

</script>

</body>

</html>

4.6.2 构造方法和this关键字

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</head>

<body>

function Person(name,age)

{

this.age=age;

this.name=name;

this.say=sayFunc;

}

function sayFunc()

{

alert(person1.name+":"+person1.age);

}

person1=new Person("王康",22);

person1.say();

</script>

</body>

</html>

4.6.3 在函数中修改参数的值

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</head>

<body>

function Person(name,age)

{

this.age=age;

this.name=name;

this.say=sayFunc;

}

function sayFunc()

{

alert(person1.name+":"+person1.age);

}

function change(p)

{

p.name="王健";

p.age=24;

}

person1=new Person("王康",22);

person1.say();

change(person1);

person1.say();

</script>

</body>

</html>

4.7 JavaScript的内部对象

4.7.1 Obetct对象

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</head>

<body>

function getAttributeValue(attr)

{

alert(person[attr]);

}

var person=new Object();

person.name="王康";

person.age=22;

getAttributeValue("name");

getAttributeValue("age");

</script>

</body>

</html>

4.7.2 String对象

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</head>

<body>

var mystr=new String("王康");

var len=mystr.length;

alert(len);

</script>

//为字符串对象中的内容加上HTML的定位标签，类似的还有big、bold

var a="This is a book";

alert(a.anchor("book"));

//charAt、charCodeAt、fontcolor

var a="This is a book";

alert(a.charAt('k'));

</script>

</body>

</html>

4.7.3 Date对象

<head>

</head>

<body>

var date=new Date();

alert(date);

var str=date.getYear()+"年";

str+=date.getMonth()+"月";

str+=date.getDate()+"日";

str+=date.getHours()+"：";

str+=date.getMinutes()+"：";

str+=date.getSeconds();

alert(str);

</script>

</body>

</html>

4.7.4 toString方法

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</head>

<body>

var x=328;

alert("hex="+x.toString(16)+"bin="+x.toString(2));

</script>

</body>

</html>

4.8 专门用于对象的语句

4.8.1 with语句

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</head>

<body>

var date=new Date();

with(date)

{

var str=getYear()+"年";

str+=getMonth()+"月";

str+=getDate()+"日";

str+=getHours()+"：";

str+=getMinutes()+"：";

str+=getSeconds();

alert(str);

}

</script>

</body>

</html>

4.8.2 for……in语句

<head>

</head>

<body>

function Person()

{

this.name="王康";

this.age=22;

this.height=175;

}

var p1=new Person();

var prop,str="";

for(prop in p1)

{

str+=prop+" ";

}

alert(str);

str="";

for(prop in p1)

{

str+=p1[prop]+" ";

}

alert(str);

</script>

</body>

</html>

4.9 数组

4.9.1 数组列表

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</head>

<body>

var arr=["王康",123,'li',3.25];

for(var i=0;i<arr.length;i++)

{

alert(arr[i]);

}

var arr=[["王康",123,'li',3.25],[34,45,56,78,98,00]]

for(var i=0;i<arr.length;i++)

{

for(var j=0;j<arr[i].length;j++)

{

alert(arr[i][j]);

}

</script>

</body>

</html>

4.9.2 用对象方式实现数组

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</head>

<body>

function MyArray()

{

this.length=arguments.length;

for(var i=0;i<this.length;i++)

{

this[i]=arguments[i];

}

var str="";

var arr=new MyArray(4,3.5,5,"fgf");

for(var i=0;i<arr.length;i++)

{

str+=arr[i]+"\n";

}

alert(str);

</script>

</body>

</html>

4.9.3 Array对象

<head>

</head>

<body>

var arr=new Array();

arr[0]=3.5;

arr[1]="王康";

arr[2]=12;

arr.sort();

var x,str="";

for(x in arr)

{

str+=x+":"+arr[x]+"\n";

}

alert(str);

</script>

</body>

</html>

4.10 思考与实践

来源：https://www.cnblogs.com/wkjs/archive/2006/08/06/2008574.html

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str函数

网页标题

date

javascript网页开发 第四章 JavaScript语法

javascript网页开发第四章 JavaScript语法