سلام
کد هاتون درسته ، فکر کنم function به نام clear از توابع اصلی جاوااسکریپت باشه ، اسمشو عوض کنی ، کار می کنه
مخصوص اعضای ویژه 
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link href="style.css" rel="stylesheet" type="text/css">
<title>Document</title>
</head>
<body>
<div></div>
<button onclick="one()">1</button>
<button onclick="two()">2</button>
<button onclick="three()">3</button>
<button onclick="plus()">+</button>
<br>
<button onclick="four()">4</button>
<button onclick="five()">5</button>
<button onclick="six()">6</button>
<button onclick="dash()">-</button>
<br>
<button onclick="seven()">7</button>
<button onclick="eight()">8</button>
<button onclick="nine()">9</button>
<button onclick="star()">*</button>
<br>
<button onclick="clearall()">C</button>
<button onclick="zero()">0</button>
<button onclick="equal()">=</button>
<button onclick="slash()">/</button>
<br>
</body>
<script src="script.js"></script>
</html>و
const div = document.getElementsByTagName("div")[0];
function one() {
div.innerHTML += "1";
}
function two() {
div.innerHTML += "2";
}
function three() {
div.innerHTML += "3";
}
function four() {
div.innerHTML += "4";
}
function five() {
div.innerHTML += "5";
}
function six() {
div.innerHTML += "6";
}
function seven() {
div.innerHTML += "7";
}
function eight() {
div.innerHTML += "8";
}
function nine() {
div.innerHTML += "9";
}
function zero() {
div.innerHTML += "0";
}
function plus() {
div.innerHTML += " + ";
}
function dash() {
div.innerHTML += " - ";
}
function star() {
div.innerHTML += " * ";
}
function slash() {
div.innerHTML += " / ";
}
function equal() {
div.innerHTML = eval(div.innerHTML);
}
function clearall() {
div.innerHTML = "1";
}
