var txt1 = document.getElementById("txt1"),
txt2 = document.getElementById("txt2"),
txt3 = document.getElementById("txt3"),
opt = document.getElementById("sel")
txt3.value = eval(txt1.value + opt.value + txt2.value)//eval函数可计算某个字符串，并执行其中的的js代码
} <input type="text" id="txt1" />
<select id="sel">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type="text" id="txt2" />
=
<input type="text" id="txt3" />
<input type="button" id="btn" value="计算" onclick="test()"/>
<HTML><HEAD>
<TITLE></TITLE>
<style type="text/css">
p {font-size: 12pt}
.red {color: redwidth:34}
.redl{color:redwidth:51}
.blue {color: bluewidth:34}
</style>
<SCRIPT LANGUAGE="JavaScript">
var Memory = 0
var Number1 = ""
var Number2 = ""
var NewNumber = "blank"
var opvalue = ""
function Display(displaynumber) {
document.calculator.answer.value = displaynumber
}
function MemoryClear() {
Memory = 0
document.calculator.mem.value = ""
}
function MemoryRecall(answer) {
if(NewNumber != "blank") {
Number2 += answer
} else {
Number1 = answer
}
NewNumber = "blank"
Display(answer)
}
function MemorySubtract(answer) {
Memory = Memory - eval(answer)
}
function MemoryAdd(answer) {
Memory = Memory + eval(answer)
document.calculator.mem.value = " M "
NewNumber = "blank"
}
function ClearCalc() {
Number1 = ""
Number2 = ""
NewNumber = "blank"
Display("")
}
function Backspace(answer) {
answerlength = answer.length
answer = answer.substring(0, answerlength - 1)
if (Number2 != "") {
Number2 = answer.toString()
Display(Number2)
} else {
Number1 = answer.toString()
Display(Number1)
}
}
function CECalc() {
Number2 = ""
NewNumber = "yes"
Display("")
}
function CheckNumber(answer) {
if(answer == ".") {
Number = document.calculator.answer.value
if(Number.indexOf(".") != -1) {
answer = ""
}
}
if(NewNumber == "yes") {
Number2 += answer
Display(Number2)
}
else {
if(NewNumber == "blank") {
Number1 = answer
Number2 = ""
NewNumber = "no"
}
else {
Number1 += answer
}
Display(Number1)
}
}
function AddButton(x) {
if(x == 1) EqualButton()
if(Number2 != "") {
Number1 = parseFloat(Number1) + parseFloat(Number2)
}
NewNumber = "yes"
opvalue = '+'
Display(Number1)
}
function SubButton(x) {
if(x == 1) EqualButton()
if(Number2 != "") {
Number1 = parseFloat(Number1) - parseFloat(Number2)
}
NewNumber = "yes"
opvalue = '-'
Display(Number1)
}
function MultButton(x) {
if(x == 1) EqualButton()
if(Number2 != "") {
Number1 = parseFloat(Number1) * parseFloat(Number2)
}
NewNumber = "yes"
opvalue = '*'
Display(Number1)
}
function DivButton(x) {
if(x == 1) EqualButton()
if(Number2 != "") {
Number1 = parseFloat(Number1) / parseFloat(Number2)
}
NewNumber = "yes"
opvalue = '/'
Display(Number1)
}
function SqrtButton() {
Number1 = Math.sqrt(Number1)
NewNumber = "blank"
Display(Number1)
}
function PercentButton() {
if(NewNumber != "blank") {
Number2 *= .01
NewNumber = "blank"
Display(Number2)
}
}
function RecipButton() {
Number1 = 1/Number1
NewNumber = "blank"
Display(Number1)
}
function NegateButton() {
Number1 = parseFloat(-Number1)
NewNumber = "no"
Display(Number1)
}
function EqualButton() {
if(opvalue == '+') AddButton(0)
if(opvalue == '-') SubButton(0)
if(opvalue == '*') MultButton(0)
if(opvalue == '/') DivButton(0)
Number2 = ""
opvalue = ""
}
</script>
</HEAD>
<BODY>
<center>
<form name="calculator">
<table bgcolor="#aaaaaa" width=230>
<tr><td>
<table bgcolor="#cccccc" border=1>
<tr><td>
<table border=0 cellpadding=0>
<tr><td bgcolor="#000080"></td></tr>
<tr><td>
<table width="100%" border=0>
<tr><td colspan=6><input type="text" readOnly name="answer" size=30 maxlength=30 onChange="CheckNumber(this.value)"></td></tr>
<tr><td colspan=6>
<table border=0 cellpadding=0>
<tr><td>
<input type="text" name="mem" size=3 maxlength=3 readOnly style="background:menu"><input type="button" name="backspace" class="redl" value="退格" onClick="Backspace(document.calculator.answer.value)return false"><input type="button" name="CE" class="redl" value="CE" onClick="CECalc()return false"><input type="reset" name="C" class="redl" value="C" onClick="ClearCalc()return false">
</td></tr>
</table>
</td></tr>
<tr><td><input type="button" name="MC" class="red" value=" MC " onClick="MemoryClear()return false"></td>
<td><input type="button" name="calc7" class="blue" value=" 7 " onClick="CheckNumber('7')return false"></td>
<td><input type="button" name="calc8" class="blue" value=" 8 " onClick="CheckNumber('8')return false"></td>
<td><input type="button" name="calc9" class="blue" value=" 9 " onClick="CheckNumber('9')return false"></td>
<td><input type="button" name="divide" class="red" value=" / " onClick="DivButton(1)return false"></td>
<td><input type="button" name="sqrt" class="blue" value="sqrt" onClick="SqrtButton()return false"></td></tr>
<tr><td><input type="button" name="MR" class="red" value=" MR " onClick="MemoryRecall(Memory)return false"></td>
<td><input type="button" name="calc4" class="blue" value=" 4 " onClick="CheckNumber('4')return false"></td>
<td><input type="button" name="calc5" class="blue" value=" 5 " onClick="CheckNumber('5')return false"></td>
<td><input type="button" name="calc6" class="blue" value=" 6 " onClick="CheckNumber('6')return false"></td>
<td><input type="button" name="multiply" class="red" value=" * " onClick="MultButton(1)return false"></td>
<td><input type="button" name="percent" class="blue" value=" % " onClick="PercentButton()return false"></td></tr>
<tr><td><input type="button" name="MS" class="red" value=" MS " onClick="MemorySubtract(document.calculator.answer.value)return false"></td>
<td><input type="button" name="calc1" class="blue" value=" 1 " onClick="CheckNumber('1')return false"></td>
<td><input type="button" name="calc2" class="blue" value=" 2 " onClick="CheckNumber('2')return false"></td>
<td><input type="button" name="calc3" class="blue" value=" 3 " onClick="CheckNumber('3')return false"></td>
<td><input type="button" name="minus" class="red" value=" - " onClick="SubButton(1)return false"></td>
<td><input type="button" name="recip" class="blue" value="1/x " onClick="RecipButton()return false"></td></tr>
<tr><td><input type="button" name="Mplus" class="red" value=" M+ " onClick="MemoryAdd(document.calculator.answer.value)return false"></td>
<td><input type="button" name="calc0" class="blue" value=" 0 " onClick="CheckNumber('0')return false"></td>
<td><input type="button" name="negate" class="blue" value="+/- " onClick="NegateButton()return false"></td>
<td><input type="button" name="dot" class="blue" value=" . " onClick="CheckNumber('.')return false"></td>
<td><input type="button" name="plus" class="red" value=" + " onClick="AddButton(1)return false"></td>
<td><input type="button" name="equal" class="red" value=" = " onClick="EqualButton()return false"></td>
</tr>
</table>
</td></tr>
</table>
</td></tr>
</table>
</td></tr>
</table>
</form>
</center>
<script language=javascript>
function keyDown()
{
var iCode=window.event.keyCode
//alert(iCode)
if(event.shiftKey)
{
switch(iCode)
{
case 56:document.all.multiply.click()break
case 59:document.all.minus.click()break
case 60:document.all.plus.click()break
}
}
if(!event.shiftKey&&!event.ctrlKey&&!event.altKey)
{
switch (iCode)
{
case 8:document.all.backspace.click()break
case 187:document.all.equal.click()break
case 96:document.all.calc0.click()break
case 97:document.all.calc1.click()break
case 98:document.all.calc2.click()break
case 99:document.all.calc3.click()break
case 100:document.all.calc4.click()break
case 101:document.all.calc5.click()break
case 102:document.all.calc6.click()break
case 103:document.all.calc7.click()break
case 104:document.all.calc8.click()break
case 105:document.all.calc9.click()break
case 110:document.all.dot.click()break
case 13:document.all.equal.click()break
case 107:document.all.plus.click()break
case 109:document.all.minus.click()break
case 106:document.all.multiply.click()break
case 111:document.all.divide.click()break
case 48:document.all.calc0.click()break
case 49:document.all.calc1.click()break
case 50:document.all.calc2.click()break
case 51:document.all.calc3.click()break
case 52:document.all.calc4.click()break
case 53:document.all.calc5.click()break
case 54:document.all.calc6.click()break
case 55:document.all.calc7.click()break
case 56:document.all.calc8.click()break
case 57:document.all.calc9.click()break
case 190:document.all.dot.click()break
case 13:document.all.equal.click()break
case 191:document.all.divide.click()break
}
}
//event.keyCode=0
//event.returnValue=false
}
window.document.attachEvent("onkeydown",keyDown)
</script>
</BODY>
</HTML>
http://www.chinadds.com
使用计算器进行混合运算的方法如下：1、有一个简单的计算器，显示屏幕比较大，而且按键比较大，比较简单，可以非常快的使用乘除混合运算。
2、可以将如下的一道题进行一次性运算：“（101*273）-（458/34）=”
3、一般来说，要先计算“（101*273）=”得出结果，并记录在纸上，用作后面使用。
4、接着将“（458/34）=”的答案计算出来，又写在纸上，并将前后的结果进行减法运算，速度比较慢，而且会出现错误的概率高。
5、采用计算器一次性计算就比较简单，充分利用好"M+"和"M-"这个按键的作用，进行混合运算。
6、按键的次序是：第一“101*273”之后，再次按住"M+"按键，接着再按“458/34”和"M-"的按键，最后按”MRS"结果就出来了，不需要用纸记录。
7、使用计算器的步骤很简单，就是要比较操作的娴熟程度，尤其要理解"M+"和"M-"\”MRS"的时候，它都是要让前面的计算结果进行了记忆并运算了。
