JavaScript基础

3.布尔类型

varx=true
vary=false

4.数组

#方式1
varcars=newArray();
cars[0]="Audi";
cars[1]="BMW";
cars[2]="Volvo";

#方式2
varcars=newArray("Audi","BMW","Volvo");

#方式3
varcars=["Audi","BMW","Volvo"];

obj.splice(n,0,val)指定位置插入元素
obj.splice(n,1,val)指定位置替换元素
obj.splice(n,1)指定位置删除元素

5.运算和比较

6.字典

varobj={key1:"value1",key2:"value2"};

obj.key1
obj.key2
或者
obj['key1']
obj['key2']

7.特殊值：Undefined和Null

其它

1.序列化

varobj={key1:"value1",key2:"value2"};
varstr='{"k1":"v1","k2":"v2"}';
vars1=JSON.stringify(obj);
vars2=JSON.parse(str);
document.write("原字典:"+obj+"<br>");
document.write("原字符串:"+str+"<br>");
document.write("序列化:"+s1+"<br>");
document.write("反序列化:"+s2+"<br>");

原字典:[objectObject]
原字符串:{"k1":"v1","k2":"v2"}
序列化:{"key1":"value1","key2":"value2"}
反序列化:[objectObject]

2.转义

varurl="https://www.sogou.com/web?query=宝强";varret=encodeURI(url);varret2=decodeURI(ret);varret3=encodeURIComponent(url);varret4=decodeURIComponent(ret3);document.write("url:"+url+"<br>");document.write("encodeURI结果:"+ret+"<br>");document.write("decodeURI结果:"+ret2+"<br>");document.write("encodeURIComponent结果:"+ret3+"<br>");document.write("decodeURIComponent结果:"+ret4+"<br>");varstr="宝强";vars1=escape(str);vars2=unescape(s1);document.write("str:"+str+"<br>")document.write("escape结果:"+s1+"<br>")document.write("unescape结果:"+s2+"<br>")

url:https://www.sogou.com/web?query=宝强encodeURI结果:https://www.sogou.com/web?query=%E5%AE%9D%E5%BC%BAdecodeURI结果:https://www.sogou.com/web?query=宝强encodeURIComponent结果:https%3A%2F%2Fwww.sogou.com%2Fweb%3Fquery%3D%E5%AE%9D%E5%BC%BA
decodeURIComponent结果:https://www.sogou.com/web?query=宝强str:宝强
escape结果:%u5B9D%u5F3A
unescape结果:宝强

3.eval

varres=eval(1+2+22/4*3)eval("vartest='fuzj'")document.write(res+"<br>")document.write(test+"<br>")效果19.5fuzj

4.时间处理

varmyDate=newDate()
注释：Date对象会自动把当前日期和时间保存为其初始值。

d=newDate();x=d.getDay();day=d.getDate();day1=d.getUTCHours();new_day=d.setMinutes(d.getMinutes()+60)document.write(d+"<br>");document.write(x+"<br>");document.write(day+"<br>");document.write(day1+"<br>");document.write(new_day+"<br>");

循环、判断和异常处理

1.条件语句判断

if(条件){}elseif(条件){}else{}如：vara=1;varb=2;if(a==b){document.write("a=b");}else{document.write("a!=b")}

switch(name){case'1':age=123;break;case'2':age=456;break;default:age=777;}如：varname='1'switch(name){case'1':age=123;break;case'2':age=456;break;default:age=777;}document.write(age)

2.循环语句

varnames=["alex","tony","rain"];for(vari=0;i<names.length;i++){console.log(i);console.log(names[i]);}varnames=["alex","tony","rain"];for(varindexinnames){console.log(index);console.log(names[index]);}while循环while(条件){//break;//continue;}

3.异常处理

try{//这段代码从上往下运行，其中任何一个语句抛出异常该代码块就结束运行}catch(e){//如果try代码块中抛出了异常，catch代码块中的代码就会被执行。//e是一个局部变量，用来指向Error对象或者其他抛出的对象}finally{//无论try中代码是否有异常抛出（甚至是try代码块中有return语句），finally代码块中始终会被执行。}thrownewError("异常内容")主动抛出异常

函数和面向对象

1.基本函数

functionfunc(arg){returntrue;}使用：functionf1(a,b){varret=a+breturnret}res=f1(10,2)document.write(res)//结果:12

varfunc=function(arg){return"tony";}使用：vartest=function(){return100}document.write(test())

(function(arg){console.log(arg);})('123')使用：(function(arg){document.write(arg)})("自制行")//这里创建了一个匿名函数(在第一个括号内)，第二个括号用于调用该匿名函数，并传入参数。

2.作用域

functionf1(){if(1==1){vartest=123}document.write(test)//无报错}f1()补充：标题之所以添加双引号是因为JavaScript6中新引入了let关键字，用于指定变量属于块级作用域

functionf1(){if(1==1){vartest=123}document.write(test)//无报错}f1()document.write(test)//报错

varname='fuzj';functionf1(){varname='f1';functionf2(){varname='f2';document.write(name)}f2()}f1()结果为：f2

varname='fuzj';functionf1(){varname='f1';functionf2(){document.write(name)}returnf2}res=f1()res()结果：f1

varname='fuzj';functionf1(){varname='f1';functionf2(){document.write(name)}varname='newf1'returnf2}res=f1()res()结果：newf1

varname='fuzj';functionf2(){document.write(name);};functionf1(){varname='f1';returnf2};res=f1()res()结果：fuzj

JavaScript中如果创建值而不赋值，则该值为undefined，如：

console.log(xxoo);

console.log(xxoo);//报错：UncaughtReferenceError:xxooisnotdefined

//输出：undefined

console.log(xo);varxo='seven';}Foo();//输出：undefined

functionf2(){vararg=[11,22];functionf3(){returnarg;}returnf3;}ret=f2();ret();

functionFoo(name,age){this.Name=name;this.Age=age;}Foo.prototype={GetInfo:function(){returnthis.Name+this.Age},Func:function(arg){returnthis.Name+arg;}}