javascript基础一

   

        //在浏览器上写入值
        document.write("啊沙发上广泛");
        //alert("it is a dialog");
        //提示用户输入值的对话框
        //var name = prompt("what is your name?","");
        //弹出对话框
        //alert( "welcome to my world " + name);
        
        //确认对话框，点击确定，返回true，点击取消，返回false
        if(confirm("are you really ok")==true)
        {
           alert("yes");
        }
        else
        {
           alert("no");
        }


 //声明变量
 <script type="text/javascript">
	     var name = 'shizhan';
	     var age =8 ;
 </script>
  
 //在浏览器中显示变量的值
 <script type="text/javascript">
        document.write("<b>name is " + name+ "</b>");
        document.write("<b>age is  " +age +  "</b>");
  </script>

   //javascript中的变量是一种宽松类型的变量，不同类型的变量之间可以相互赋值
    <script type="text/javascript">
       var item ="shizhan";
       item = 20;
       item = 13.2;
       item = true;
       item = null;
       alert(item);
     </script>
    
    //不同类型的变量可以互相赋值
     <script>
       var item = 23;
       var a = "sas";
       a = item;
       alert(a);
    </script>

    var string ="5+4";
    var num1 = eval(str);
    alert(num1);

    //javascript的switch，case结构
     <script>
      var color = "red";
      switch(color)
      {
         case "red":
           alert("hot");
           break;
         case "blue":
           alert("cold");
           break;
         default:
           alert("not a good choice");
           break;
      }
    </script>