Skip to content

Simple calculator in HTML and JavaScript

I have to write a calculator in HTML. I really can’t find what is going wrong and it does not show the results. I can’t find something wrong can you help? I’m running it in Chrome.

JavaScript File and and the HTML:

showresult(choise){
var n1=parsefloat(document.getElementById('num1').value);
var n2=parsefloat(document.getElementById('num2').value);
var r;
var c=choise;

switch(c)
	{
	case '1':
		r=n1+n2;
		break;
	case '2':
		r=n1-n2;
		break;
	case '3':
		r=n1*n2;
		break;
	case '4': 
		r=n1/n2;
		break;
	case '5':
		r=n2*100/n1;
		break;
	default:
		break;
			
	}
document.getElementById('result').innerHTML=r;

	

}
<!DOCTYPE html>
<html>
<head>
<title>Calculator</title>
<script src="calculator.js" type="text/javascript"></script>
</head>
<body>


<h1>My calculator</h1>
<table border="1" cellpadding="5" cellspacing="5" width="600">
<tr align="center">
<td>First number</td>
<td>Second Number</td>
<td>Result</td>
</tr>
<tr align="center">
<td><input name="number1" type="text" size=10 id='num1'/></td>
<td><input name="number2" type="text" size=10 id='num2'/></td>
<td> <input type="text" id='result' readonly ></td>
</tr>
<tr>
<td colspan="3">
<button onclick="showresult('1')">+</button>
<button onclick="showresult('2')">-</button>
<button onclick="showresult('3')">*</button>
<button onclick="showresult('4')">/</button>
<button onclick="showresult('5')">%</button>
</td>
</tr>

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

Answer

Things to fix: 1) Assign to value, not innerHTML, when referring to an input element. (They have no content, hence no innerHTML. 2) Start a function declaration with the keyword function. 3) It’s parseFloat, not parsefloat. JavaScript is case-sensitive.

Minimally fixed code:

function showresult(choise){
var n1=parseFloat(document.getElementById('num1').value);
var n2=parseFloat(document.getElementById('num2').value);
var r;
var c=choise;

switch(c)
	{
	case '1':
		r=n1+n2;
		break;
	case '2':
		r=n1-n2;
		break;
	case '3':
		r=n1*n2;
		break;
	case '4': 
		r=n1/n2;
		break;
	case '5':
		r=n2*100/n1;
		break;
	default:
		break;
			
	}
document.getElementById('result').value=r;

	

}
<!DOCTYPE html>
<html>
<head>
<title>Calculator</title>
<script src="calculator.js" type="text/javascript"></script>
</head>
<body>


<h1>My calculator</h1>
<table border="1" cellpadding="5" cellspacing="5" width="600">
<tr align="center">
<td>First number</td>
<td>Second Number</td>
<td>Result</td>
</tr>
<tr align="center">
<td><input name="number1" type="text" size=10 id='num1'/></td>
<td><input name="number2" type="text" size=10 id='num2'/></td>
<td> <input type="text" id='result' readonly ></td>
</tr>
<tr>
<td colspan="3">
<button onclick="showresult('1')">+</button>
<button onclick="showresult('2')">-</button>
<button onclick="showresult('3')">*</button>
<button onclick="showresult('4')">/</button>
<button onclick="showresult('5')">%</button>
</td>
</tr>

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