学着做了一个简单的计算器！记录记录！哈哈
<!DOCTYPE html>
<html>
<head>
<title>简单的计算器</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
input{width:100%}
</style>
</head>
<body>
<script type="text/javascript">
function compute(obj)
{
obj.expr.value=eval(obj.expr.value)
}
var plus="+";
var minus="-";
var multiply="*";
var divide="/";
var decimal=".";
function enter(obj,string)
{
obj.expr.value+=string;
}
function cle(obj)
{
obj.expr.value='';
}
</script>
<form >
<table border=1>
<tr >
<td colspan="4"><input type="text" name="expr" size="30" style="width:97%"></td>
</tr>
<tr>
<td><input type="button" value="7" οnclick="enter(this.form,7)"></td>
<td><input type="button" value="8" οnclick="enter(this.form,8)"></td>
<td><input type="button" value="9" οnclick="enter(this.form,9)"></td>
<td><input type="button" value="/" οnclick="enter(this.form,divide)"></td>
</tr>
<tr>
<td><input type="button" value="4" οnclick="enter(this.form,4)"></td>
<td><input type="button" value="5" οnclick="enter(this.form,5)"></td>
<td><input type="button" value="6" οnclick="enter(this.form,6)"></td>
<td><input type="button" value="*" οnclick="enter(this.form,multiply)"</td>
</tr>
<tr>
<td><input type="button" value="1" οnclick="enter(this.form,1)"></td>
<td><input type="button" value="2" οnclick="enter(this.form,2)"></td>
<td><input type="button" value="3" οnclick="enter(this.form,3)"></td>
<td><input type="button" value="-" οnclick="enter(this.form,minus)"></td>
</tr>
<tr>
<td colspan="2"><input type="button" value="0" οnclick="enter(this.form,0)"></td>
<td><input type="button" value="." οnclick="enter(this.form,decimal)"></td>
<td><input type="button" value="+" οnclick="enter(this.form,plus)"></td>
</tr>
<tr>
<td colspan="2" ><input type="button" value="=" οnclick="compute(this.form)" ></td>
<td colspan="2"><input type="button" value="AC" size=3 οnclick="cle(this.form)"></td>
</tr>
</table>
</form>
</body>
</html>