JavaScript实现随机变色网页计算器示例

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
 <TITLE> Day 2 </TITLE>
 <META NAME="Generator" CONTENT="EditPlus">
 <META NAME="Author" CONTENT="">
 <META NAME="Keywords" CONTENT="">
 <META NAME="Description" CONTENT="">
 <script>
  function calculator(){
    var selection=document.form.selection.value;
    var numb1=document.form.number1.value;
    var numb2=document.form.number2.value;
 var relnum="";
    switch(selection){
      case "+":
        relnum=parseFloat(numb1)+parseFloat(numb2);
  break;
      case '-':
        relnum=numb1 - numb2;
        break;
      case '*': 
        relnum=numb1 * numb2;
        break;
      case '/':
        if(numb2==0)
          alert("wrong input! ");
        relnum=numb1 / numb2;
        break;
      case '%':
        relnum=numb1 % numb2;
        break;
      }
  document.form.result.value=relnum;
  }
  function sound(){
    document.all.sound.src="clock.wav";
    }
  function changeBgcolor(){
    var bgc=document.getElementById("idbgc");
    var rand="";
    for(var i=0;i<6;i++){
    rand+=Math.round(Math.random()*9)
    }
    bgc.style.backgroundColor='#'+rand;
  }  
  </script>
 </HEAD>
 <BODY bgcolor="aliceblue" id="idbgc">
  <h1>simple web calculator</h1>
  <form name="form" action=""> 
    <input type=text name="number1" style="width:80px ">
    <select name="selection">
      <option value='+'>&nbsp;+&nbsp;<option>
      <option value='-'>-<option>
      <option value='*'>*<option>
      <option value='/'>/<option>
      <option value='%'>%<option>
    </select>
    <input type=text name="number2" style="width:80px ">
    <input type="button" value="&nbsp;=&nbsp;" onclick="calculator(),changeBgcolor()">
    <input type=text name="result" style="width:80px "><br>
    <input type="reset" value="reset" onclick="changeBgcolor()">
  </form>
 </BODY>
</HTML>