JavaScript实现加减乘除运算的完整示例

<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
</head>
<script language="javascript" type="text/javascript">
//除法函数
function accDiv(arg1,arg2){
  var t1 = 0, t2 = 0, r1, r2, n;
  try
  {
    t1 = arg1.toString().split(".")[1].length;
  }
  catch(e)
  {t1 = 0;}
  try
  {
    t2 = arg2.toString().split(".")[1].length;
  }
  catch(e)
  {t2 = 0;}
  with(Math)
  {
    r1 = Number(arg1.toString().replace(".",""));
    r2 = Number(arg2.toString().replace(".",""));
    n = Math.max(t1,t2);
    return (r1/r2)*pow(10, t2-t1);
  }
}

//乘法函数
function accMul(arg1,arg2)
{
  var t1 = 0, t2 = 0, r1, r2;
  try
  {
    t1 = arg1.toString().split(".")[1].length;
  }
  catch(e)
  {t1 = 0;}
  try
  {
    t2 = arg2.toString().split(".")[1].length;
  }
  catch(e)
  {t2 = 0;}
  with(Math)
  {
    r1 = Number(arg1.toString().replace(".",""));
    r2 = Number(arg2.toString().replace(".",""));
    return (r1*r2)/pow(10, t2+t1);
  }
}

//加法函数
function accAdd(arg1,arg2){
  var t1 = 0, t2 = 0, m;
  try
  {
    t1 = arg1.toString().split(".")[1].length;
  }
  catch(e)
  {t1 = 0;}
  try
  {
    t2 = arg2.toString().split(".")[1].length;
  }
  catch(e)
  {t2 = 0;}
  with(Math)
  {
    m=Math.pow(10,Math.max(t1,t2));
    return (arg1 * m + arg2 * m) / m;
  }
}

//减法函数
function accSubtr(arg1,arg2){
  var t1 = 0, t2 = 0, m, n;
  try
  {
    t1 = arg1.toString().split(".")[1].length;
  }
  catch(e)
  {t1 = 0;}
  try
  {
    t2 = arg2.toString().split(".")[1].length;
  }
  catch(e)
  {t2 = 0;}
  with(Math)
  {
    //动态控制精度长度
    n = Math.max(t1,t2);
    m = Math.pow(10, n);
    //return (arg1 * m - arg2 * m) / m;
    return ((arg1 * m - arg2 * m) / m).toFixed(n);
  }
}


//给String类型增加一个div方法，调用起来更加方便。
String.prototype.div = function (arg){
  return accDiv(this, arg);
}

//给String类型增加一个mul方法，调用起来更加方便。
String.prototype.mul = function (arg){
  return accMul(arg,this);
}

//给String类型增加一个add方法，调用起来更加方便。
String.prototype.add = function (arg){
  return accAdd(arg,this);
}

//给String类型增加一个subtr方法，调用起来更加方便。
String.prototype.subtr = function (arg){
  return accSubtr(this, arg);
}


function cal()
{
  var arg1 = document.Form1.TextBox1.value;
  var arg2 = document.Form1.TextBox2.value;
  //document.Form1.TextBox5.value = accDiv(arg1, arg2);
  //document.Form1.TextBox6.value = accMul(arg1, arg2);
  //document.Form1.TextBox7.value = accAdd(arg1, arg2);
  //document.Form1.TextBox8.value = accSubtr(arg1, arg2);

  document.Form1.TextBox5.value = arg1.div(arg2);
  document.Form1.TextBox6.value = arg1.mul(arg2);
  document.Form1.TextBox7.value = arg1.add(arg2);
  document.Form1.TextBox8.value = arg1.subtr(arg2);
}
</script>

<body>
<form id="Form1" name="Form1" method="post" runat="server">
<div style="border:solid 1px #000000; width:600px;">
 <div style="float:left; width:30%;"><input id="TextBox1" type="text" value="0" name="TextBox1" /></div>
 <div style="float:left; width:30%;"><input id="TextBox2" value="0" type="text" name="TextBox2" /></div>
 <div style="float:left; width:30%;">
  <div>accDiv：<input id="TextBox5" type="text" name="TextBox5" /></div>
  <div>accMul：<input id="TextBox6" type="text" name="TextBox6" /></div>
  <div>accAdd：<input id="TextBox7" type="text" name="TextBox7" /></div>
  <div>accSubtr：<input id="TextBox8" type="text" name="TextBox8" /></div>
 </div>
 <div style="float:right; width:10%;"><input type="button" name="aa" value="cal" onclick="cal();" /></div>
</div>
</form>
</body>
</html>