用javascript写计算器
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>计算器</title>
<script type="text/javascript">
var FKeyPad = document.Keypad;
var Accum = 0;
var FlagNewNum = false;
var PendingOp = "";
//数字键控制函数
function NumPressed(Num) {
if (FlagNewNum)
{
document.Keypad.ReadOut.value = Num;
FlagNewNum = false;
}
else
{
if (document.Keypad.ReadOut.value == "0")
document.Keypad.ReadOut.value = Num;
else
document.Keypad.ReadOut.value += Num;
}
}
//加、减、乘、除、等号键被按下时执行该函数
function Operation(Op)
{PendingOp = Op;
var Readout = document.Keypad.ReadOut.value;
if (FlagNewNum && PendingOp != "=");
else
{
FlagNewNum = true;
if ( '+' == PendingOp )
Accum += parseFloat(Readout);
else if ( '-' == PendingOp )
Accum -= parseFloat(Readout);
else if ( '/' == PendingOp )
Accum /= parseFloat(Readout);
else if ( '*' == PendingOp )
Accum *= parseFloat(Readout);
else
Accum= parseFloat(Readout);
document.Keypad.ReadOut.value = Accum;
}
}
//按下小数点时执行该函数
function Decimal()
{
var curReadOut = document.Keypad.ReadOut.value;
if (FlagNewNum)
{
curReadOut = "0.";
FlagNewNum = false;
}
else
{
if (curReadOut.indexOf(".") == -1)
curReadOut += ".";
}
document.Keypad.ReadOut.value = curReadOut;
}
//当CE键被按下时执行该函数,将当前输入的数清除
function ClearEntry()
{
document.Keypad.ReadOut.value = "0";
FlagNewNum = true;
}
//当C键被按下时执行该函数,将计算器恢复到初始状态
function Clear()
{
Accum = 0;
PendingOp = "";
ClearEntry();
}
//[+/-]按钮按下时执行该函数,将当前输入取相反数
function Neg()
{
document.Keypad.ReadOut.value = parseFloat(document.Keypad.ReadOut.value) * -1;
}
//[%]键按下时执行该函数
function Percent()
{
document.Keypad.ReadOut.value = (parseFloat(document.Keypad.ReadOut.value) / 100) * parseFloat(Accum);}
</script>
</head>
<body>
<center>
<form name="Keypad" action="">
<table>
<tr>
<td colspan="3">
<input name="ReadOut" type="Text" size=24 value="0" width=100%>
</td>
<td><input name="btnClear" type="Button" value=" C " onclick="Clear()"></td>
<td><input name="btnClearEntry" type="Button" value="CE " onclick="ClearEntry()"></td>
</tr>
<tr></tr>
<tr>
<td><input name="btnOne" type="Button" value=" 1 " onclick="NumPressed(1)"></td>
<td><input name="btnTwo" type="Button" value=" 2 " onclick="NumPressed(2)"></td>
<td><input name="btnThree" type="Button" value=" 3 " onclick="NumPressed(3)"></td>
<td><input name="btnPlus" type="Button" value=" + " onclick="Operation('+')"></td>
<td><input name="btnMinus" type="Button" value=" - " onclick="Operation('-')"></td>
</tr>
<tr>
<td><input name="btnFive" type="Button" value=" 4 " onclick="NumPressed(4)"></td>
<td><input name="btnFive" type="Button" value=" 5 " onclick="NumPressed(5)"></td>
<td><input name="btnFive" type="Button" value=" 6 " onclick="NumPressed(6)"></td>
<td><input name="btnMultiply" type="Button" value=" * " onclick="Operation('*')"></td>
<td><input name="btnDivide" type="Button" value=" / " onclick="Operation('/')"></td>
</tr>
<tr>
<td><input name="btnSeven" type="Button" value=" 7 " onclick="NumPressed(7)"></td>
<td><input name="btnSeven" type="Button" value=" 8 " onclick="NumPressed(8)"></td>
<td><input name="btnSeven" type="Button" value=" 9 " onclick="NumPressed(9)"></td>
<td><input name="btnNeg" type="Button" value=" +/- " onclick="Neg()"></td>
<td><input name="btnPercent" type="Button" value=" % " onclick="Percent()"></td>
</tr>
<tr>
<td><input name="btnZero" type="Button" value=" 0 " onclick="NumPressed(0)"></td>
<td colspan="3"><input name="btnDecimal" type="Button" value=" . " onclick="Decimal()"></td>
<td><input name="btnEquals" type="Button" value=" = " onclick="Operation('=')"></td>
</tr>
</table>
</form>
</center>
</body>
</html>
注意点:
- 页面采用table布局
- FlagNewNum是用来控制是否由新的数
- 从文本框中取出来的值相当于字符串,直接加上+num就可以了
- 进行计算时用:parseFloat将字符串转为浮点数