simpleCalculator2.html

<html>

<head>
	<script type="text/JavaScript">
		function get(eid) {return document.getElementById(eid);};
		function calculate(op){
			var a = parseFloat(get('a').value);
			var b = parseFloat(get('b').value);
			if (isNaN(a) || isNaN(b)) {
				alert('both inputs must be numbers');
				return;
			}
			var answer = a + op + b + ' = ' + eval('a' + op + 'b');
			get('resultAsTextBox').value = answer;
		}
	</script>
</head>

<body>
	<form>
		<p>
			Instructions:<br />
			Type two numbers and click a button.<br />
			The answer will then appear below.<br /><br />
			Input values:<br/ >
			First number to include: = <input id="a" type="text" /><br />
			Second number to include: = <input id="b" type="text" /><br /><br />
			<input type="button" value=" + " onclick="calculate(this.value)" />
			<input type="button" value=" - " onclick="calculate(this.value )" />
			<input type="button" value=" * " onclick="calculate(this.value)" />
			<input type="button" value=" / " onclick="calculate(this.value)" /><br />
			Output value:<br />
			Result= <input type="text" id="resultAsTextBox" size="50" disabled="disabled" />
		<p>
	</form>
</body>

</html>