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Write a javascript program to make a simple calculator

Question Posted / mehta fenil & bodiwala rum

Answer Posted / mehta fenil & bodiwala rum

<html>
<head>
<title>Basic Calculator</title>
<script language="JavaScipt" type="text/JavaScript">
var adddigit=false;
var oldval=0;
var op="=";

function btnconcat(c)
{
if(adddigit)
{
document.getElementById("txtdisplay").value+=c;
}
else
{
document.getElementById("txtdisplay").value=c;
adddigit=true;
}
}

function operation(newop)
{
var newarg=eval(document.getElementById("txtdisplay").value)
if(op=="+")
{
oldval=oldval+newarg;
}
else if(op=="-")
{
oldval=oldval-newarg;
}
else if(op=="*")
{
oldval=oldval*newarg;
}
else if(op=="/")
{
oldval=oldval/newarg;
}
else if(op=="=")
{
oldval=newarg;
}
else
{
oldval=newarg;
}
document.getElementById("txtdisplay").value=oldval;
adddigit=false;
op=newop;
}

function backspace()
{

document.getElementById("txtdisplay").value=document.getElementById("txtdisplay").value.substring(0,document.getElementById("txtdisplay").value.length*1-1);
}

function btnce()
{
document.getElementById("txtdisplay").value="";
}

function btnc()
{
document.getElementById("txtdisplay").value=0;
oldval=0;
adddigit=false;
op="=";
}
</script>
</head>
<body>
<center>
<table border=5 cellpading=5 cellspacing=5>

<tr>
<td colspan="4"><input type="text" id="txtdisplay"
size="25" style="text-align:right"></td>
</tr>

<tr>
<td>
<center>
<input type="button" id="btnc" value="C"
onClick="btnc();">
</center>
</td>

<td>&nbsp;

</td>

<td>
<center>
<input name="Button" type="button" id="btnc"
onClick="btnce();" value="CE">
</center>
</td>

<td>
<center>
<input type="button" id="btnc" value="<="
onClick="backspace();">
</center>
</td>
</tr>

<tr>
<td>
<center>
<input type="button" id="btn7" value="7"
onClick="btnconcat(7);">
</center>
</td>

<td>
<center>
<input type="button" id="btn8" value="8"
onClick="btnconcat(8);">
</center>
</td>

<td>
<center>
<input type="button" id="btn9" value="9"
onClick="btnconcat(9);">
</center>
</td>

<td>
<center>
<input type="button" id="btnpls" value="+"
onClick="operation('+');">
</center>
</td>
</tr>

<tr>
<td>
<center>
<input type="button" id="btn4" value="4"
onClick="btnconcat(4);">
</center>
</td>

<td>
<center>
<input type="button" id="btn5" value="5"
onClick="btnconcat(5);">
</center>
</td>

<td>
<center>
<input type="button" id="btn6" value="6"
onClick="btnconcat(6);">
</center>
</td>

<td>
<center>
<input type="button" id="btnmin" value="-"
onClick="operation('-');">
</center>
</td>
</tr>

<tr>
<td>
<center>
<input type="button" id="btn1" value="1"
onClick="btnconcat(1);">
</center>
</td>

<td>
<center>
<input type="button" id="btn2" value="2"
onClick="btnconcat(2);">
</center>
</td>

<td>
<center>
<input type="button" id="btn3" value="3"
onClick="btnconcat(3);">
</center>
</td>

<td>
<center>
<input type="button" id="btnmul" value="*"
onClick="operation('*');">
</center>
</td>
</tr>

<tr>
<td>
<center>
<input type="button" id="btnpoi" value="."
onClick="btnconcat('.');">

</center>
</td>

<td>
<center>
<input type="button" id="btn0" value="0"
onClick="btnconcat(0);">
</center>
</td>

<td>
<center>
<input type="button" id="btneql" value="="
onClick="operation(value)">
</center>
</td>

<td>
<center>
<input type="button" id="btndiv" value="/"
onClick="operation('/');">
</center>
</td>
</tr>

</table>
</center>
</body>
</html>

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