JavaScript基础

switch

   
     

    
       
    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      
 
 var seson 
    
      =
    
       prompt(
    
      "
    
      请输入数字（1～4）
    
      "
    
      );
 
    
      switch
    
       (seson) {
 
    
      case
    
       
    
      "
    
      1
    
      "
    
      : msg 
    
      =
    
       
    
      "
    
      你选择的春天
    
      "
    
      ; 
    
      break
    
      ;
 
    
      case
    
       
    
      "
    
      2
    
      "
    
      : msg 
    
      =
    
       
    
      "
    
      你选择的夏天
    
      "
    
      ; 
    
      break
    
      ;
 
    
      case
    
       
    
      "
    
      3
    
      "
    
      : msg 
    
      =
    
       
    
      "
    
      你选择的秋天
    
      "
    
      ; 
    
      break
    
      ;
 
    
      case
    
       
    
      "
    
      4
    
      "
    
      : msg 
    
      =
    
       
    
      "
    
      你选择的冬天
    
      "
    
      ; 
    
      break
    
      ;
 
    
      default
    
      : msg 
    
      =
    
       
    
      "
    
      你选择的不对
    
      "
    
      ; 
    
      break
    
      ;
 }
 document.write(msg);

 
    
      </
    
      script
    
      >
   
     

多个函数同时调用

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 function fun1(){
 alert(
    
      "
    
      这是fun1
    
      "
    
      ); 
 }
 function fun2(){
 alert(
    
      "
    
      这是fun2
    
      "
    
      );
 }

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
    
      

    
      </
    
      head
    
      >
    
      

    
      <
    
      body
    
      >
    
      

    
      <
    
      input type
    
      =
    
      "
    
      button
    
      "
    
       value
    
      =
    
      "
    
      单击我
    
      "
    
       onClick
    
      =
    
      "
    
      fun1(),fun2()
    
      "
    
      >
    
      

    
      </
    
      body
    
      >
   
     

绝对值函数的应用

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 document.write(
    
      "
    
      0的绝对值为：
    
      "
    
      ,Math.abs(
    
      0
    
      ),
    
      "
    
      <br>
    
      "
    
      );
 document.write(
    
      "
    
      1的绝对值为：
    
      "
    
      ,Math.abs(
    
      1
    
      ),
    
      "
    
      <br>
    
      "
    
      );
 document.write(
    
      "
    
      -1的绝对值为：
    
      "
    
      ,Math.abs(
    
      -
    
      1
    
      ),
    
      "
    
      <br>
    
      "
    
      );

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
   
     

try catch处理

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 
    
      try
    
      {
 a[
    
      1
    
      ] 
    
      =
    
       
    
      10
    
      ;
 }
    
      catch
    
      (e){
 alert(
    
      "
    
      错误:
    
      "
    
      +
    
      e);
 }

    
      -->
    
      

    
      </
    
      script
    
      >
   
     

连接两个数组

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 a 
    
      =
    
       
    
      new
    
       Array(
    
      "
    
      a
    
      "
    
      ,
    
      "
    
      b
    
      "
    
      ,
    
      "
    
      c
    
      "
    
      );
 b 
    
      =
    
       
    
      new
    
       Array(
    
      1
    
      ,
    
      2
    
      ,
    
      3
    
      );
 c 
    
      =
    
       a.concat(b);
 
 
    
      for
    
      (i
    
      =
    
      0
    
      ;i
    
      <
    
      c.length;i
    
      ++
    
      ){
 document.write(c[i],
    
      "
    
      <br>
    
      "
    
      );
 }

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
   
     

平方根函数的使用

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 n 
    
      =
    
       prompt(
    
      "
    
      请输入一个要平方根的数：
    
      "
    
      );
 document.write(n,
    
      "
    
      的平方根为:
    
      "
    
      ,Math.sqrt(n));

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
   
     

得到一个数的平方

   
     

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 radius 
    
      =
    
       prompt(
    
      "
    
      请输入一个数：
    
      "
    
      );
 area 
    
      =
    
      Math.pow(radius, 
    
      2
    
      );
 document.write(
    
      "
    
      这个数的平方是:
    
      "
    
       
    
      +
    
       area);

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
   
     

取得对象的信息

   
     

    
      <
    
      body
    
      >
    
      

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 function showID(obj){
 alert(obj.id);
 }

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
    
      

    
      <
    
      input type
    
      =
    
      "
    
      button
    
      "
    
       value 
    
      =
    
      "
    
      显示
    
      "
    
       id
    
      =
    
      "
    
      bt
    
      "
    
       onClick
    
      =
    
      "
    
      showID(this)
    
      "
    
      >
    
      

    
      </
    
      body
    
      >
   
     

取整函数的使用

   
     

    
      <
    
      body
    
      >
    
      

    
      <
    
      script language
    
      =
    
      "
    
      javascript
    
      "
    
      >
    
      

    
      <!--
    
      
 n 
    
      =
    
       prompt(
    
      "
    
      请输入一个要取整的数：
    
      "
    
      );
 
    
      if
    
      (n
    
      >
    
      0
    
      ){
 
    
      int
    
       
    
      =
    
       Math.floor(n);
 }
    
      else
    
      {
 
    
      int
    
       
    
      =
    
       Math.ceil(n);
 }
 document.write(n,
    
      "
    
      的整数为:
    
      "
    
      ,
    
      int
    
      );

    
      //
    
      -->
    
      

    
      </
    
      script
    
      >
    
      

    
      </
    
      body
    
      >
   
     

取得类别名称

   
     

    
      <
    
      style type
    
      =
    
      "
    
      text/css
    
      "
    
      >
    
      

    
      <!--
    
      
 .bgcolor{
 background
    
      -
    
      color:#
    
      993300
    
      ;
}

    
      -->
    
      

    
      </
    
      style
    
      >
    
      

    
      </
    
      head
    
      >
    
      

    
      <
    
      body
    
      >
    
      

    
      <
    
      input type
    
      =
    
      "
    
      button
    
      "
    
       value 
    
      =
    
      "
    
      显示
    
      "
    
       id
    
      =
    
      "
    
      bt
    
      "
    
       onClick
    
      =
    
      "
    
      alert
    
      

    
      (bt.className)
    
      "
    
       class=
    
      "
    
      bgcolor
    
      "
    
      >
    
      

    
      </
    
      body
    
      >