A java script program to make a simple calculator

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A java script program to make a simple calculator

 

<html>
<head>
<title>A simple JavaScript calculator</title>
<script language='JavaScript'>
Default = "0";
Current = "0";
Operation = 0;
MaxLength = 30;

function AddDigit(dig) {
if (Current.indexOf("!") == -1) {
if ((eval(Current) == 0) && (Current.indexOf(".") == -1)) {
Current = dig;
} else {
Current = Current + dig;
}
Current = Current.toLowerCase();
} else {
Current = "Hint! Press 'AC'";
}
if (Current.indexOf("e0") != -1) {
var epos = Current.indexOf("e");
Current = Current.substring(0,epos+1) + Current.substring(epos+2);
}
if (Current.length > MaxLength) {
Current = "Too long";
}
document.Calculator.Display.value = Current;
}

function Dot() {
if ( Current.length == 0) {
Current = "0.";
} else {
if (( Current.indexOf(".") == -1) && (Current.indexOf("e") == -1)) {
Current = Current + ".";
}
}
document.Calculator.Display.value = Current;
}

function DoExponent() {
if ( Current.indexOf("e") == -1 ) {
Current = Current + "e0";
document.Calculator.Display.value = Current;
}
}

function PlusMinus() {
if(Current.indexOf("e") != -1) {
var epos = Current.indexOf("e-");
if (epos != -1) {
Current = Current.substring(0,1+epos) + Current.substring(2+epos);
} else { epos = Current.indexOf("e");
Current = Current.substring(0,1+epos) + "-" + Current.substring(1+epos);
}
} else {
if ( Current.indexOf("-") == 0 ) {
Current = Current.substring(1);
} else {
Current = "-" + Current;
}
if ((eval(Current) == 0) && (Current.indexOf(".") == -1 )) {
Current = "0"; }
}
document.Calculator.Display.value = Current;
}

function Clear() {
Current = "0";
document.Calculator.Display.value = Current;
}

function AllClear() {
Current = "0";
Operation = 0;
Default = "0";
document.Calculator.Display.value = Current;
}

function Operate(op) {
if (Operation != 0) { Calculate(); };
if (op.indexOf("*") > -1) { Operation = 1; };
if (op.indexOf("/") > -1) { Operation = 2; };
if (op.indexOf("+") > -1) { Operation = 3; };
if (op.indexOf("-") > -1) { Operation = 4; };

Default = Current;

Current = "";
document.Calculator.Display.value = Current;
}

function Calculate() {
if (Operation == 1) { Current = eval(Default) * eval(Current); };
if (Operation == 2) {
if (eval(Current) != 0) {
Current = eval(Default) / eval(Current)
} else {
Current = "Divide by zero";
}
}
if (Operation == 3) { Current = eval(Default) + eval(Current); };
if (Operation == 4) { Current = eval(Default) - eval(Current); };
Operation = 0;
Default = "0";
Current = Current + "";
if (Current.indexOf("Infinity") != -1) {
Current = "Value too big";
}
if (Current.indexOf("NaN") != -1) {
Current = "I don't understand";
}
document.Calculator.Display.value = Current;
}

function FixCurrent() {
Current = document.Calculator.Display.value;
Current = "" + parseFloat(Current);
if (Current.indexOf("NaN") != -1) {
Current = "I don't understand";
}
document.Calculator.Display.value = Current;
}
</script>

</head>
<hr><div align="center">
<FORM name="Calculator">
<table width="40%" height="40%" border="4" bgcolor="#FFEBCD"><tr>
<td colspan="2" align="center">
<b><font face="Verdana, Arial, Helvetica" color="#000080" size="3">
A Simple JavaScript Calculator<br></font>
<font face="Courier" size="5">
<input type="text" maxlength="40" size="25" name="Display" onChange="FixCurrent()">
</font></b>
</td></tr>
<tr><td width="65%" align="center">
<table><tr>
<td><input type="button" name="seven" value=" 7 " OnClick="AddDigit('7')"></td>
<td><input type="button" name="eight" value=" 8 " OnClick="AddDigit('8')"></td>
<td><input type="button" name="nine" value=" 9 " OnClick="AddDigit('9')"></td>
</tr><tr>
<td><input type="button" name="four" value=" 4 " OnClick="AddDigit('4')"></td>
<td><input type="button" name="five" value=" 5 " OnClick="AddDigit('5')"></td>
<td><input type="button" name="six" value=" 6 " OnClick="AddDigit('6')"></td>
</tr><tr>
<td><input type="button" name="one" value=" 1 " OnClick="AddDigit('1')"></td>
<td><input type="button" name="two" value=" 2 " OnClick="AddDigit('2')"></td>
<td><input type="button" name="three" value=" 3 " OnClick="AddDigit('3')"></td>
</tr><tr>
<td><input type="button" name="plusmin" value=" +/- " OnClick="PlusMinus()"></td>
<td><input type="button" name="one" value=" 0 " OnClick="AddDigit('0')"></td>
<td><input type="button" name="two" value=" . " OnClick="Dot()"></td>
</tr>
</table>
</td>
<td width="35%" align="center">
<table><tr>
<td><input type="button" name="clear" value=" C " OnClick="Clear()"></td>
<td><input type="button" name="AC" value=" AC " OnClick="AllClear()"></td>
</tr><tr>
<td><input type="button" name="mul" value=" * " OnClick="Operate('*')"></td>
<td><input type="button" name="div" value=" / " OnClick="Operate('/')"></td>
</tr><tr>
<td><input type="button" name="add" value=" + " OnClick="Operate('+')"></td>
<td><input type="button" name="sub" value=" - " OnClick="Operate('-')"></td>
</tr><tr>
<td><input type="button" name="result" value=" = " OnClick="Calculate()"></td>
<td align="right"><input type="button" name="exp" value=" EXP " OnClick="DoExponent()"></td>
</tr></table>
</td>
</tr></table>
</div></body>
</html>   







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