A Pen by Zachary Churchill on CodePen.
Created
August 11, 2020 05:45
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<html> | |
<head> | |
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> | |
<link rel="stylesheet" href="https://unpkg.com/sakura.css/css/sakura.css" type="text/css"> | |
<style> | |
button { | |
width:50px; | |
height:50px; | |
border-radius: 50%; | |
} | |
.calc { | |
border: 2px solid gray; | |
} | |
#res { | |
background: #f4eded; | |
border: 2px solid gray; | |
} | |
</style> | |
</head> | |
<body> | |
<div> | |
<h1>Calculon</h1> | |
<table class="calc" style="width:40%"> | |
<tbody><tr> | |
<td id="res" colspan="3"> 0 </td> | |
<td> <button data-type="op" id="div"> ÷ </button> </td> | |
</tr> | |
<tr> | |
<td> <button data-type="num" id="7"> 7 </button> </td> | |
<td> <button data-type="num" id="8"> 8 </button> </td> | |
<td> <button data-type="num" id="9"> 9 </button> </td> | |
<td> <button data-type="op" id="mul"> × </button> </td> | |
</tr> | |
<tr> | |
<td> <button data-type="num" id="4"> 4 </button> </td> | |
<td> <button data-type="num" id="5"> 5 </button> </td> | |
<td> <button data-type="num" id="6"> 6 </button> </td> | |
<td> <button data-type="op" id="sub"> − </button> </td> | |
</tr> | |
<tr> | |
<td> <button data-type="num" id="1"> 1 </button> </td> | |
<td> <button data-type="num" id="2"> 2 </button> </td> | |
<td> <button data-type="num" id="3"> 3 </button> </td> | |
<td> <button data-type="op" id="add"> + </button> </td> | |
</tr> | |
<tr> | |
<td colspan="2"> <button data-type="num" id="0"> 0 </button> </td> | |
<td> <button data-type="dec" id="dec"> . </button> </td> | |
<td> <button data-type="op" id="eq"> = </button> </td> | |
</tr> | |
</tbody></table> | |
</div> | |
<script src="index.js"></script> | |
</body> | |
</html> |
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// mutable state | |
let buffer = 0 | |
let decimalPlace = 0 | |
let next = addDigit | |
let calc = document.querySelector('.calc') | |
function reset(resolve) { | |
calc.addEventListener('click', (e) => calcEv(e, resolve), { once: true }) | |
} | |
async function calcEv(e, resolve) { | |
const x = buffer | |
switch (e.target.getAttribute('data-type')) { | |
case 'num': | |
update(next(e.target.id)) | |
reset(resolve) | |
break; | |
case 'dec': | |
next = addDecimal | |
reset(resolve) | |
break; | |
case 'op': | |
switch (e.target.id) { | |
case 'add': { | |
next = addDigit | |
decimalPlace = 0 | |
update(0) | |
const y = await op() | |
resolve(x + y) | |
break; | |
} | |
case 'sub': { | |
next = addDigit | |
decimalPlace = 0 | |
update(0) | |
const y = await op() | |
resolve(x - y) | |
break; | |
} | |
case 'mul': { | |
next = addDigit | |
decimalPlace = 0 | |
update(0) | |
const y = await op() | |
resolve(x * y) | |
break; | |
} | |
case 'div': { | |
next = addDigit | |
decimalPlace = 0 | |
update(0) | |
const y = await op() | |
resolve(x / y) | |
if (y == 0) { | |
calcError("Undefined") | |
} | |
break; | |
} | |
case 'eq': { | |
next = addDigit | |
decimalPlace = 0 | |
resolve(buffer) | |
reset(resolve) | |
break; | |
} | |
} | |
break; | |
default: | |
reset(resolve) | |
} | |
} | |
function op() { | |
return new Promise( resolve => { | |
const g = (x) => { | |
update(x) | |
resolve(x) | |
} | |
const f = (e) => calcEv(e, g) | |
calc.addEventListener('click', f, { once: true }) | |
}) | |
} | |
reset(update) | |
function update(x) { | |
if (numDigits(x) > 10) { | |
calcError("Error") | |
} else { | |
buffer = x | |
document.getElementById('res').innerHTML = buffer; | |
} | |
} | |
function calcError(x) { | |
buffer = 0 | |
document.getElementById('res').innerHTML = x; | |
} | |
function getNum() { | |
return new Promise(resolve => { | |
document.querySelectorAll('.num').forEach(button => { | |
button.addEventListener('click', () => { | |
resolve(Number(button.id)) | |
}) | |
}) | |
}) | |
} | |
function addDigit(id) { | |
return (buffer * 10) + Number(id) | |
} | |
function addDecimal(id) { | |
decimalPlace += 1 | |
let decimals = Number(id) / Math.pow(10,decimalPlace) | |
let res = buffer + decimals | |
console.log(res) | |
return res | |
} | |
function numDigits(x) { | |
return Math.max(Math.floor(Math.log10(Math.abs(x))), 0) + 1; | |
} |
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