Untitled

<!DOCTYPE html>
<html>
<head>
	<link href="css/main.css" rel="stylesheet" type="text/css">
	<title>Calculator</title>

</head>
<body>
<form name="Calc">
	<input type="text" name="display" size="16" id="display">
	<button type="button" name="clear" id="clear" class="equation" onclick="allclear()">
		AC
	</button>
	<button type="button" name="pos-neg" id="pos-neg" class="equation" value="" onclick="posneg()">
		+/-
	</button>
	<button type="button" name="average" id="average" class="equation" value="avg" onclick="avg()">
		avg
	</button>
	<button type="button" name="divide" id="divide" class="equation" value="/" onclick="Calc.display.value += ' / '">
		/
	</button>
	<button type="button" name="seven" id="seven" class="number" value="7" onclick="Calc.display.value += '7'">
		7
	</button>
	<button type="button" name="eight" id="eight" class="number" value="8" onclick="Calc.display.value += '8'">
		8
	</button>
	<button type="button" name="nine" id="nine" class="number" value="9" onclick="Calc.display.value += '9'">
		9
	</button>
	<button type="button" name="multiply" id="multiply" class="equation" value="*" onclick="Calc.display.value += ' * '">
		*
	</button>
	<button type="button" name="four" id="four" class="number" value="4" onclick="Calc.display.value += '4'">
		4
	</button>
	<button type="button" name="five" id="five" class="number" value="5" onclick="Calc.display.value += '5'">
		5
	</button>
	<button type="button" name="six" id="six" class="number" value="6" onclick="Calc.display.value += '6'">
		6
	</button>
	<button type="button" name="subtract" id="subtract" class="equation" value="-" onclick="Calc.display.value += ' - '">
		-
	</button>
	<button type="button" name="one" id="one" class="number" value="1" onclick="Calc.display.value += '1'">
		1
	</button>
	<button type="button" name="two" id="two" class="number" value="2" onclick="Calc.display.value += '2'">
		2
	</button>
	<button type="button" name="three" id="three" class="number" value="3" onclick="Calc.display.value += '3'">
		3
	</button>
	<button type="button" name="add" id="add" class="equation" value="+" onclick="Calc.display.value += ' + '">
		+
	</button>
	<button type="button" name="zero" id="zero" class="number" value="0" onclick="Calc.display.value += '0'">
		0
	</button>
	<button type="button" name="point" id="point" class="number" value="." onclick="Calc.display.value += '.'">
		.
	</button>
	<button type="button" name="equals" id="equals" class="equals" value="=" onclick="Calc.display.value = eval(Calc.display.value)">
		=
	</button>
</form>

<script type="text/javascript">
var input = [];

function avg() {
	let a = document.getElementById('display').value;
	input.push(a);
	input.split();
}

function allclear() {
	input = [];
	Calc.display.value = input;
}

function posneg() {
	let a = document.getElementById('display').value;
	a =- a;
	Calc.display.value = a;
}
</script>
</body>
</html>