用HTML 做这样一个计算器，怎么编写javascript的部分。

试试这段代码

<script language=JavaScript>

var opStack = new Array(4)

opStack[0] = 0

opStack[1] = ''

opStack[2] = ''

opStack[3] = ''

function StartCal(){

document.PAD.SUM.value= "0"

}

function KeyinNum() {

if (opStack[0] >= 2) { opStack[0] = 3 }

else { opStack[0] = 1 }

opStack[opStack[0]] = '' + document.PAD.SUM.value

}

function resetNum () {

opStack[0] = 0

opStack[1] = 0

document.PAD.CAL.value = ''

document.PAD.SUM.value = '0'

}

function calc1 (x) {

var opFlag = opStack[0]

if (opFlag == -1 || opFlag == 1) { count(x) }

else if (opFlag == 3) {

opStack[1] = '' + eval(opStack[1] + opStack[2] + opStack[3])

count(x) }

}

function count (x) {

if (x == 'Si') { opStack[1] = '' + Math.sin (opStack[1]) }

else if (x == 'aS') { opStack[1] = '' + Math.asin(opStack[1]) }

else if (x == 'Co') { opStack[1] = '' + Math.cos (opStack[1]) }

else if (x == 'aC') { opStack[1] = '' + Math.acos(opStack[1]) }

else if (x == 'Ta') { opStack[1] = '' + Math.tan (opStack[1]) }

else if (x == 'aT') { opStack[1] = '' + Math.atan(opStack[1]) }

else if (x == '≡') { opStack[1] = '' + Math.pow (opStack[1],.5) }

else if (x == '^2') { opStack[1] = '' + Math.pow (opStack[1], 2) }

else if (x == '^3') { opStack[1] = '' + Math.pow (opStack[1], 3) }

else if (x == '^4') { opStack[1] = '' + Math.pow (opStack[1], 4) }

else if (x == 'AB') { opStack[1] = '' + Math.abs (opStack[1])}

else if (x == '∽') { }

document.PAD.CAL.value = ''

opStack[0] = -1

display()

document.PAD.SUM.focus()

document.PAD.SUM.select()

}

function display () {

var sum = parseFloat(opStack[1])

document.PAD.SUM.value = '' + Math.round (sum * Math.pow(10,14)) / Math.pow(10,14)

}

function fra(){

var i

var j = 1

var k = document.PAD.SUM.value

if (k >= 70) {opStack[1] = 0document.PAD.SUM.value = "---Error---"return}

for (i = 1i <= ki++){j = j * i}

opStack[1] = document.PAD.SUM.value = j

document.PAD.SUM.focus()

document.PAD.SUM.select()

}

function entry (x) {

if (opStack[0] == -1) { opStack[0] = 1opStack[1] = ''}

if (opStack[0] == 0) { opStack[0] = 1opStack[1] = ''}

if (opStack[0] == 2) { opStack[0] = 3opStack[3] = ''}

var result = result = opStack[opStack[0]]

if (result == '0'){ result = '' }

if (x>='1' &&x<='9') { result = '' + result + x }

else if (x == 'P') { result = '' + Math.PI }

else if (x == '0') { if (result != '') result = '' + result + '0' }

else if (x == 'B') { if (result != '') result = result.substring(0, result.length - 1) }

else if (x == '.') {

if (result != '') { if (result.indexOf(".") == -1) result += "." }

else{ result = '0.'} }

if (result =='') result = '0'

opStack[opStack[0]] = result

document.PAD.SUM.value = result

}

function calc2 (x) {

var opFlag = opStack[0]

if (opFlag != 2) {

if (opFlag == 3) {

opStack[1]=''+eval(opStack[1]+opStack[2]+opStack[3])

display()}

opStack[0] = 2

opStack[2] = x

document.PAD.CAL.value = x

document.PAD.SUM.focus()

document.PAD.SUM.select() }

}

function neg() {

if (opStack[0] != 2 &&opStack[0] != 0) {

opStack[0] = Math.abs(opStack[0])

var result = opStack[opStack[0]]

if (result != '0' &&result != '') {

if (result.charAt(0) == '-') { result = result.substring(1, result.length) }

else { result = '-' + result }

opStack[opStack[0]] = result

document.PAD.SUM.value = result } }

}

function TurnOff(){

var ask = confirm("您确定要关闭计算器么？")

if (ask == true) {window.close()}

else {return}

}

</script>

<FORM NAME="PAD">

<TABLE BORDER>

<TR><TD COLSPAN=8>

<INPUT NAME="CAL" TYPE="TEXT" SIZE=1 VALUE="">结果：

<INPUT NAME="SUM" TYPE="TEXT" SIZE=16 VALUE="" onChange="KeyinNum()">

<TR>

<TD><INPUT TYPE="BUTTON" VALUE="重置" onClick="resetNum()">

<TD><INPUT TYPE="BUTTON" VALUE="开方" onClick="calc1('≡')">

<TD><INPUT TYPE="BUTTON" VALUE="平方" onClick="calc1('^2')">

<TD><INPUT TYPE="BUTTON" VALUE="X !" onClick="fra()" >

<TR>

<TD><INPUT TYPE="BUTTON" VALUE=" 7 " onClick="entry('7')">

<TD><INPUT TYPE="BUTTON" VALUE=" 8 " onClick="entry('8')">

<TD><INPUT TYPE="BUTTON" VALUE=" 9 " onClick="entry('9')">

<TD><INPUT TYPE="BUTTON" VALUE=" * " onClick="calc2('*')">

<TR>

<TD><INPUT TYPE="BUTTON" VALUE=" 4 " onClick="entry('4')">

<TD><INPUT TYPE="BUTTON" VALUE=" 5 " onClick="entry('5')">

<TD><INPUT TYPE="BUTTON" VALUE=" 6 " onClick="entry('6')">

<TD><INPUT TYPE="BUTTON" VALUE=" / " onClick="calc2('/')">

<TR>

<TD><INPUT TYPE="BUTTON" VALUE=" 1 " onClick="entry('1')">

<TD><INPUT TYPE="BUTTON" VALUE=" 2 " onClick="entry('2')">

<TD><INPUT TYPE="BUTTON" VALUE=" 3 " onClick="entry('3')">

<TD><INPUT TYPE="BUTTON" VALUE=" - " onClick="calc2('-')">

<TR>

<TD><INPUT TYPE="BUTTON" VALUE=" 0 " onClick="entry('0')">

<TD><INPUT TYPE="BUTTON" VALUE=" . " onClick="entry('.')">

<TD><INPUT TYPE="BUTTON" VALUE="+/-" onClick="neg()">

<TD><INPUT TYPE="BUTTON" VALUE=" + " onClick="calc2('+')">

<TR>

<TD><INPUT TYPE="BUTTON" VALUE="关闭" onClick="TurnOff()">

<TD><INPUT TYPE="BUTTON" VALUE="后退" onClick="entry('B')">

<TD><INPUT TYPE="BUTTON" VALUE=" Pi "onClick="entry('P')">

<TD><INPUT TYPE="BUTTON" VALUE=" = " onClick="calc1('=')" >

</TABLE>

</FORM>

我这里有一个现成的，自己再改一下吧（<HTML>

<HEAD>

<SCRIPT LANGUAGE = "JavaScript">

function calcu(){

var numb1= document.calc.num1.value

var numb2= document.calc.num2.value

var total= parseFloat(numb1)*parseFloat(numb2)

document.calc.result.value=total

}

</SCRIPT>

<script type="text/javascript" language="JavaScript1.2" src="menu.js"></script>

</HEAD>

<BODY>

<FORM name="calc">

<P><BR>

<font size="5">会说话的QQ竞拍喽！</fo

<BR>

竟拍价?

<INPUT name="num2" TYPE="text" id="num2" value="120" size="15"><BR>

购买数量：

<INPUT TYPE="text" name="num1" size="15"> <BR>

预计总价：

<INPUT name="result" TYPE="text" size="15">

</P>

<P>

<INPUT name="getAnswer" TYPE="button" id="getAnswer" onClick="calcu()"

value="计算看看"><!--单机鼠标调

</P>

</FORM>

</BODY>

</HTML>

）

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