该计算器功能： 1.校验：小数点，重复计算，以及大量更符合用户体验的操作。 2.能够从键盘输入。
效果图：
HTML代码：
<Meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Insert title here
<input type="button" class="button" name="deleteAll" value="C" onclick="clearAllText()" /><input type="button" class="button" name="opposite" value="+/-" onclick="oppositeOp()" /><input type="button" class="button" name="delOne" value="←" onclick="deleteOneDigit()" /><input type="button" class="button" name="Add" value="+" onclick="clickOperation('+')" /><input type="button" class="button" name="seven" value="7" onclick="clickNum(7)" /><input type="button" class="button" name="eight" value="8" onclick="clickNum(8)" /><input type="button" class="button" name="nine" value="9" onclick="clickNum(9)" /><input type="button" class="button" name="Reduce" value="-" onclick="clickOperation('-')" /><input type="button" class="button" name="Four" value="4" onclick="clickNum(4)" /><input type="button" class="button" name="Five" value="5" onclick="clickNum(5)" /><input type="button" class="button" name="Sex" value="6" onclick="clickNum(6)" /><input type="button" class="button" name="Multip" value="x" onclick="clickOperation('x')" /><input type="button" class="button" name="One" value="1" onclick="clickNum(1)" /><input type="button" class="button" name="Two" value="2" onclick="clickNum(2)" /><input type="button" class="button" name="Three" value="3" onclick="clickNum(3)" /><input type="button" class="button" name="Division" value="÷" onclick="clickOperation('/')" /><input type="button" class="button" name="opposite" value="√" onclick="more()" /><input type="button" class="button" name="Zero" value="0" onclick="clickNum(0)" /><input type="button" class="button" name="Point" value="." onclick="clickNum('.')" /><input type="button" class="button" name="Equal" value="=" onclick="calcu()" /></div></form>
<script type="text/javascript" src="./js/jquery-1.7.2.min.js">
<script type="text/javascript" src="./js/calcu.js">
css代码：
js代码：
function show() {
cal.display = "block";
}
function hide() {
cal.display = "none";
}
function clearAllText() {
upText.value = "";
downText.value = "0";
opFlag = false;
checkEqual = false;
}
function oppositeOp(){
downText.value = -downText.value;
}
function deleteOneDigit() {
downText.value = downText.value.substring(0,downText.value.length - 1);
if (downText.value == "" || (downText.value.charAt(0) == "-" && downText.value.charAt(1) == "")) {
downText.value = "0";
return downText.value;
}
return downText.value;
}
function clickNum(num) {
if(num == ".") {
checkIfAddPoint(num);
} else {
checkIfAddNum(num);
}
checkEqual = false;
}
function checkIfAddPoint(num) {
if((num=="." && downText.value == "0") || opFlag == true) {
downText.value="0.";
opFlag = false;
} else if(num == "." && downText.value.indexOf(".") > -1) {
downText.value;
} else {
downText.value += num;
}
}
function checkIfAddNum(num) {
if((num != "." && downText.value == "0" && downText.value[1] != ".")
|| opFlag == true
|| downText.value == "Infinity"
|| checkEqual == true) {
downText.value = num;
opFlag = false;
} else {
downText.value += num;
}
}
function clickOperation(op){
checkEqual = false;
downText.value = checkdownTextValid(downText.value);
downText.value = checkZero(upText.value,downText.value);
switch(op){
case "+":{
upText.value = appendupTextValue(upText.value,downText.value,"+");
opFlag = true;
}break;
case "-":{
upText.value = appendupTextValue(upText.value,"-");
opFlag = true;
}break;
case "x":{
upText.value = appendupTextValue(upText.value,"*");
opFlag = true;
}break;
case "/":{
upText.value = appendupTextValue(upText.value,"/");
opFlag = true;
}break;
}
}
function checkdownTextValid(downText){
if(downText.charAt(downText.length-1) == "."){
return downText.substring(0,downText.length-1);
}
return downText;
}
function checkZero(upText,downText){
if(upText.charAt(upText.length-1) == "/" && downText == "0"){
return "Error";
}
return downText;
}
function appendupTextValue(oldvalue,newvalue,operation){
if(oldvalue == ""){
return oldvalue = newvalue+operation;
} else if(opFlag!=true){
return oldvaluee = oldvalue+newvalue+operation;
} else{
return oldvalue.substring(0,oldvalue.length-1)+operation;
}
}
function calcu() {
if(!checkEqual){
downText.value = eval(upText.value+downText.value);
upText.value = "";
checkEqual = true;
}
}
window.document.onkeydown = chooseKey;
function chooseKey(evt){
if(evt.keyCode == 13){alert("=");}
else if(evt.keyCode == 8){deleteOneDigit();}
else if(evt.keyCode == 27){clearAllText();}
else if(evt.keyCode == 48){clickNum('0');}
else if(evt.keyCode == 49){clickNum('1');}
else if(evt.keyCode == 50){clickNum('2');}
else if(evt.keyCode == 51){clickNum('3');}
else if(evt.keyCode == 52){clickNum('4');}
else if(evt.keyCode == 53){clickNum('5');}
else if(evt.keyCode == 54){clickNum('6');}
else if(evt.keyCode == 55){clickNum('7');}
else if(evt.keyCode == 56){clickNum('8');}
else if(evt.keyCode == 57){clickNum('9');}
else if(evt.keyCode == 96){clickNum('0');}
else if(evt.keyCode == 97){clickNum('1');}
else if(evt.keyCode == 98){clickNum('2');}
else if(evt.keyCode == 99){clickNum('3');}
else if(evt.keyCode == 100){clickNum('4');}
else if(evt.keyCode == 101){clickNum('5');}
else if(evt.keyCode == 102){clickNum('6');}
else if(evt.keyCode == 103){clickNum('7');}
else if(evt.keyCode == 104){clickNum('8');}
else if(evt.keyCode == 105){clickNum('9');}
else if(evt.keyCode == 110){clickNum('.');}
else if(evt.keyCode == 106){clickOperation('x');}
else if(evt.keyCode == 107){clickOperation('+');}
else if(evt.keyCode == 111){clickOperation('÷');}
else if(evt.keyCode == 109){clickOperation('-');}
